Devoured while lost in time and space
I think that you are right because of the unspoken rule of cooperative games. I could not find anything in the erratas apart from a reference to "move".




  You are unaffected by other game effects […] 


This does imply that the investigator cannot have any effects at all. So they cannot be a target for anything at all: spells, Dark Pacts, etc… 

This is again implied by the errata, although it refers to "moves" and not other specific effects.


  Q. Can an investigator with a Lost in Time and Space Condition
  be moved by another investigator using the Plumb the Void Spell? 
  
  A. No. If an effect states that an investigator cannot move,
  such as a Lost in Time and Space Condition or a Detained
  Condition, that investigator cannot move on his own nor can
  he be moved by any effect.