 campaign is geographically the closest to the events of LMOP, taking place in the Dessarin Valley, which is just south of Triboar--only a few days' travel from Phandalin

A:

Yes, there is one in a published module
In Tomb of Annihilation (ToA), there is

 The Ring of Winter

That item is carried by an NPC and other NPC's are searching for it. (FWIW, I think it will dovetail into SKT nicely - but that's personal opinion).  It has potential world-wide implication if certain parties get their hands on it.  It is "missing" in the sense that two groups of NPCs want it, and another NPC (who is nearly impossible to find except by random encounter) has it in their possession.  
It is a very powerful item to the extent that in Adventurer's League, during public play, that item will be confiscated/removed from a player who ends up with it on their character sheet if they end up with it during play. We have a Q&A on that here.  Caution: there are spoilers.    
The trouble with it being absent.
For one thing, it is mentioned in the Storm King's Thunder adventure as being absent in the introduction.  Its absence informs a piece of the back story for a key faction in the adventure: the Frost Giants.   

 In the introduction, the motivations for the Frost Giant Jarl (king) is shows that recovery of the Ring of Winter is one of his prime objectives.  He wants that artifact to bring back a kind of Ice Age in the North. His problem is that the means he has used to track it down - using a drop of blood from the last person known to have it - has created a red herring.  His agents are tracking down relatives of the person who has it, not the person themselves.  In other words, based on the lore up to the time of SKT, the Jarl will never find it.    

ToA was published after the SKT adventure, which changes the lore(continuity) and thus the chances of the artifact being found, as well as the means by which it may be found.   
Our ToA group ran into a two powerful groups of NPCs (well, more powerful than our party by quite a bit as it turned out) who were looking for that item specifically.  We
campaign is geographically the closest to the events of LMOP, taking home in the Dessarin Valley, which is barely south of Triboar -- only a few days' travel from Phandalin 

 A: 

 Yes, there be one in a published module 
 In Tomb of Annihilation (ToA), there be 

  The Ring of Winter 

 That detail is carried by an NPC and other NPC's are searching for it. (FWIW, I think it will dovetail into SKT nicely - but that's personal impression).   It has potential earth - broad implication if certain parties get their hands on it.   It is " miss " in the sense that two groups of NPCs desire it, and another NPC (who is nearly impossible to find except by random brush) has it in their monomania.  
 It is a very powerful item to the extent that in Adventurer's League, during public play, that item will be confiscated / murder from a player who ends up with it on their character sheet if they end up with it during play. We have a Q&A on that here.   Caution: there are spoilers.    
 The trouble with it being absent. 
 For one thing, it is mentioned in the Storm King's Thunder adventure as being absent in the introduction.   Its absence informs a part of the back story for a cardinal cabal in the adventure: the Frost Giants.   

  In the introduction, the motivations for the Frost Giant Jarl (king) is shows that convalescence of the Ring of Winter is one of his prime aim.   He wants that artifact to bring back a kind of Ice Age in the North. His trouble is that the means he has used to track it down - using a drop of blood from the last person known to have it - has created a red herring.   His agents are track down relative of the person who has it, not the person themselves.   In other words, based on the lore up to the time of SKT, the Jarl will never rule it.    

 ToA was published after the SKT adventure, which changes the lore(continuity) and thus the chance of the artifact being found, as well as the means by which it may be found.   
 Our ToA group run into a two powerful group of NPCs (well, more powerful than our party by quite a spot as it turned out) who were look for that item specifically.   We
 calpaign is geographically the closest to the evxnts of LMOP, taying place in the Dessarin Vellet, whixh is just south of Trkboar--only a few dqys' uravel from Phandemin

A:

Yes, there ls onz mn a published kodule
In Tmmb of Annihildtkou (ToA), there is

 The Ring of Winter

Thae item os carried by an NPC wnd knhtr NPC's are searching for it. (FWIW, I thinn it will dovrtail into SKT nicely - but thah's personal opinioj).  It has piteneual world-widd implicatpmn if certzin parties get their hands on kt.  Ic is "missint" un hve sense thet two groups of NIBs want it, and another NPC (wmo is neqrly impossible to fiid except by random gncounter) vaa it in their poswewsion.  
It is x vefy kowxrfhl itel tk the exteht that in Qdventurer's League, cuwpmg public plzy, thae ytem will be confiscated/removed from a klayed who ends up with it ob their character shegt if they end up with it during play. We have a Q&A on that vere.  Zauuiin: thdee are spoilers.    
The trouble with it being abfsnu.
Fog one thing, it is mentioned on tng Storm King's Jhunder adbenture as being ahsent ig the introducuion.  Its absence informs a piecw of the bach story for a key fcction in thz advemture: the Frost Giants.   

 In the introductiln, the mofkvations for the Frpsd Giant Jarl (king) is shows that reciverv of the Rinb of Wynter is oje of his prime objectivfs.  Hg wantv that artlfact to bring back a kind of Irx Age in the Mosth. His proylem ix that the mewns he has useb to traek it aown - usinf a dro' of blood fwom the last [grson known tm have ie - hqs ceeated x red herring.  Nis agents are tracjing down relativex ow the person who haw it, not the petsov trelsxlves.  In other wosds, casdc on ghe lort ui tu thr time of SKT, the Jasl wjll never find it.    

ToA was publishqd after the XKT adventure, whicj chaiges tie lorr(cogtinuity) and thus the chances kf the arhifwct being fotnd, qs well as tke means by which it may be found.   
Our VoA group ran into a twi powerful groups oy KPCs (well, moce powqrful that our party by quite a bit as it turntd out) who were looking for tvat ihem specifically.  We
campaign is geographically the closest to the LMOP, place in Dessarin Valley, which a days' travel from A: Yes, there one in a published module In of Annihilation (ToA), there is The Ring of Winter That item is carried an NPC and other NPC's are searching for it. (FWIW, I think it dovetail SKT - that's personal opinion). It has potential world-wide implication if certain parties get their hands on it. is "missing" in the sense that two groups NPCs want it, and NPC (who is nearly impossible find by random has in possession. It is very powerful item to the extent that in Adventurer's League, during public play, that item will be from a ends up it their sheet if they with it during play. We have that here. Caution: there are spoilers. The trouble it being For one thing, it is mentioned the Storm King's Thunder adventure as being absent the introduction. Its absence informs a piece of the back story for a key faction adventure: the Frost Giants. the introduction, the for Frost Jarl is shows recovery of the Ring of Winter is one of his prime He wants that artifact to bring back a kind of in North. His problem that the means he used track it down - drop blood person to it - has created red herring. His agents are down relatives of the the person themselves. In other words, based on lore up to the time of SKT, Jarl will never find it. ToA was published after the SKT adventure, changes the thus the chances of the artifact being found, well as the means which it may be found. Our ToA group ran a powerful groups NPCs (well, more than our party quite a bit turned out) were for We
 campaign is geographically tHe closest tO the eVenTs oF LmOP, tAkinG place in the DesSArin valley, which is just south Of TriBoAR--onlY A fEw dayS' travel FRoM pHanDaLiN

A:

YEs, THeRe is oNe iN a publiShed module
in TOmB of AnnihilatIOn (toA), there is

 the ring of Winter

thaT item iS cArrIEd by aN NPc and oTher NPc'S are seArching foR iT. (fWIW, I tHInk it wiLL DoVetaIl into SKT nicely - buT ThAT's personal opinIon).  It hAs POtENTiaL woRld-wide impLiCatioN If certaIN pARTIes GEt their hands oN it.  It is "missINg" iN the seNsE thAT two grOups oF Npcs wAnt it, and anoTher nPC (who is nEarly iMPossiblE To find eXcept bY raNdoM encOUnTeR) haS iT In tHEiR poSSesSion.  
It is A vErY poweRful ITEM To thE exTent That iN Adventurer's LEagUe, duRIng PubliC play, That ItEm wilL be conFiscaTeD/removed from a plAyer Who ends up WitH iT on ThEir chARacter SheEt iF they enD up with IT duRiNG PLaY. We have a Q&A on that heRe.  cAUtIon: there Are spoILeRs.    
tHe troublE wIth It beING abseNt.
FoR OnE thing, it Is mentIOnEd In the StOrM King's thUndEr aDventURe as Being aBsent in tHe intROduction.  Its absENce informs a piECe OF ThE Back StoRy for a key faCtioN In thE advENtUre: THe FroSt GiaNtS.   

 in THe introduction, the moTiVationS for tHe Frost Giant JArl (king) is sHOWS that recOverY Of THe Ring of Winter Is one Of his prime OBjectiveS.  He waNts that aRtifact to BRIng back a KinD of ice age IN ThE North. His probLEM is tHaT the meaNs hE has useD to TraCk iT doWn - Using a droP of blood FrOm ThE lAst PersoN Known to hAvE it - HaS crEated A Red herRing.  HIs agEnTs ARe tRacking DOwN RElatIvEs Of thE peRsOn who Has iT, Not The persOn themselVes.  iN othEr WoRds, baseD on the lore up tO tHe time of SKt, tHe JArl wilL NEver find It.    

ToA was published after tHE SKT advEntUre, whIch cHanges the LorE(contiNuiTY) and thUs the cHanceS oF thE ARtifaCT BeIng FoUnd, as well aS THe mEans bY wHich It may be Found.   
Our ToA group raN IntO a two powerful GroUps oF npCS (weLL, mORe pOwERfuL THan our party by quIte a bit as iT tURnEd out) who weRE loOkIng for tHat item SpeciFIcally.  WE
 campaign is geographicall y the clos est t o t heev ents  ofLMOP, taking p l acein the Dessarin Valley , whi ch is j u st  sout h of Tr i bo a r --o nl ya f ew da ys' t rav el from  Phandalin 

A :
Yes, therei sone in a p ubl ished module 
In  Tombof  An n ihila tio n (To A), th e re is
 The Rin go f Wint e r

That i te m is  carried by an NP C  a n d other NPC'sare se ar c hi n g  fo r i t. (FWIW,Ithink it will do v e t ail into SKT nice ly - but th a t's  perso na l o p inion) .  It  h a s p otential wo rld- wide impl icatio n  if cer t ain par ties g etthe ir h a nd sonit .   I t  i s " m iss ing" inth esense  tha t t w o gr oup s of  NPCs  want it, and  an othe r  NP C (wh o isnear ly  impo ssible  to f in d except by ran domencounter ) h as  it  i n the i r poss ess ion .  
Itis a ve r y p ow e r f ul  item to the exten tt h at  in Adve nturer ' sLe a gue, dur in g p ubli c play,  tha t  i tem will  be co n fi sc ated/re mo ved fr om  apla yer w h o en ds upwith iton th e ir character s h eet if they e n du p  w i th i t d uring play.  Weh avea Q& A  o n t h at he re. Ca u ti o n: there are spoile rs .    The t rouble with i t being ab s e n t.
For o ne t h in g , it is mentio ned i n the Stor m  King'sThund er adven ture as b e i ng absen t i n t heint r o du ction.  Its a b s ence  i nformsa p iece of  th e b ack  st or y for a k ey facti on  i nth e a dvent u re: theFr ost  G ian ts. 

 Inthe i ntro du ct i on,  the mo t iv a t ions  f or  the  Fr os t Gia nt J a rl(king)is showstha t  rec ov er y of th e Ring of Win te r is one o fhis  prime o bjective s.  He wants that artif a ct to b rin g bac k akind of I ceAge in  th e  North . Hisprobl em  is t hat t h e  m ean she has use d totrack  i t do wn - us ing a drop of bloo d  fr om the last p ers on k n o wn  to ha v e i t-  ha s created a red h erring.  H is ag ents are t r ack in g downrelativ es of the per son who h as it, no tthep e rso n themselv es.  Inother wor d s, ba s ed  on t helore u ptothe t ime of SKT , the  Jarlwi ll nev er fi nd  it.   

ToA was published aft er the  SKTadv enture, w hic h  ch anges the  lor e(continui ty)  an d thu s t h e cha nces of  th e  arti fact being fou n d,  as w el l as the me a n s  by  whic h i t  may b e fo und.   
Our ToA g r oup ran into a  two p owe rfu l  gro up s of NPCs (wel l,mo r e  powerfu lthan our pa rty by q ui t e a b it asit tur ned out ) wh o  werelook ing  for that  it em specifi ca ll y .  We
 campaign_is geographically_the closest to the_events of_LMOP,_taking place_in_the Dessarin Valley,_which is just_south of Triboar--only a_few days' travel_from_Phandalin

A:

Yes, there is one in a published module
In Tomb of Annihilation (ToA), there is

_The_Ring of_Winter

That_item_is carried by an NPC_and other NPC's are searching_for it._(FWIW, I think it will dovetail into SKT_nicely_- but that's_personal opinion).  It has potential world-wide implication if_certain parties get their hands on_it.  It_is_"missing"_in the sense that_two groups of NPCs want it,_and another NPC (who is nearly_impossible to find except by random encounter)_has it in their possession. _
It is a very powerful_item to_the extent that in Adventurer's_League, during public_play, that_item will be_confiscated/removed from a player who ends_up with it_on their character sheet if they_end_up with it_during_play._We have_a Q&A on_that_here. _Caution:_there are spoilers.   _
The_trouble with it being absent.
For one thing,_it is mentioned in_the_Storm King's Thunder adventure_as being absent in the_introduction.  Its absence informs a_piece of_the back_story for a key faction in the adventure: the Frost Giants._  

 In the introduction,_the motivations for the_Frost Giant_Jarl_(king) is shows_that_recovery of_the Ring of Winter is one of_his prime_objectives.  He wants that artifact_to bring back a_kind_of Ice Age in the North._His problem is that the means_he has used to track_it_down_- using a drop of_blood from the last person known_to have it_- has created a red herring. _His_agents are tracking down relatives of_the_person who has it, not the_person_themselves._ In other words, based_on the lore up to the_time of SKT, the Jarl will never find it._  _

ToA was published after the_SKT_adventure,_which changes the lore(continuity) and thus the chances of the_artifact being_found, as well_as the means by which it may be found. _ 
Our ToA group ran into a_two powerful groups of NPCs (well, more powerful than our party_by quite a bit as it turned out)_who were looking for that item specifically._ We