Is skydiving not NOTAMed in the US?
14 CFR 105 covers parachute operations in the USA.

There is not a requirement for a NOTAM, but since this happened at an uncontrolled airport the nearest ATC facility must be notified at least 1 hour in advance but not more than 24 hours in advance and, they must have approval from airport management.

Then for the actual jump, ATC must be notified at least 5 minutes prior to jump via radio from the aircraft.




  §105.23   Parachute operations over or onto airports.
  
  No person may conduct a parachute operation, and no pilot in command
  of an aircraft may allow a parachute operation to be conducted from
  that aircraft, over or onto any airport unless—
  
  (a) For airports with an operating control tower:
  
  (1) Prior approval has been obtained from the management of the
  airport to conduct parachute operations over or on that airport.
  
  (2) Approval has been obtained from the control tower to conduct
  parachute operations over or onto that airport.
  
  (3) Two-way radio communications are maintained between the pilot of
  the aircraft involved in the parachute operation and the control tower
  of the airport over or onto which the parachute operation is being
  conducted.
  
  (b) For airports without an operating control tower, prior approval
  has been obtained from the management of the airport to conduct
  parachute operations over or on that airport.
  
  (c) A parachutist may drift over that airport with a fully deployed
  and properly functioning parachute if the parachutist is at least
  2,000 feet above that airport's traffic pattern, and avoids creating a
  hazard to air traffic or to persons and property on the ground.
  
  §105.25   Parachute operations in designated airspace.
  
  (a) No person may conduct a parachute operation, and no pilot in
  command of an aircraft may allow a parachute operation to be conducted
  from that aircraft—
  
  (1) Over or within a restricted area or prohibited area unless the
  controlling agency of the area concerned has authorized that parachute
  operation;
  
  (2) Within or into a Class A, B, C, D airspace area without, or in
  violation of the requirements of, an air traffic control authorization
  issued under this section;
  
  (3) Except as provided in paragraph (c) and (d) of this section,
  within or into Class E or G airspace area unless the air traffic
  control facility having jurisdiction over the airspace at the first
  intended exit altitude is notified of the parachute operation no
  earlier than 24 hours before or no later than 1 hour before the
  parachute operation begins.
  
  (b) Each request for a parachute operation authorization or
  notification required under this section must be submitted to the air
  traffic control facility having jurisdiction over the airspace at the
  first intended exit altitude and must include the information
  prescribed by §105.15(a) of this part.
  
  (c) For the purposes of paragraph (a)(3) of this section, air traffic
  control facilities may accept a written notification from an
  organization that conducts parachute operations and lists the
  scheduled series of parachute operations to be conducted over a stated
  period of time not longer than 12 calendar months. The notification
  must contain the information prescribed by §105.15(a) of this part,
  identify the responsible persons associated with that parachute
  operation, and be submitted at least 15 days, but not more than 30
  days, before the parachute operation begins. The FAA may revoke the
  acceptance of the notification for any failure of the organization
  conducting the parachute operations to comply with its requirements.
  
  (d) Paragraph (a)(3) of this section does not apply to a parachute
  operation conducted by a member of an Armed Force within a restricted
  area that extends upward from the surface when that area is under the
  control of an Armed Force.


Even more information is available in AC 105-2E.