The two approaches I am considering:
- Make a routine to added to the adjective property array of any object that can be picked up by an NPC. Have the routine return the word "his" or "her" or "its" based on the NPC's gender and whether the object is in a character's possession.
- Make a verb grammar that uses a routine as a grammar token to verify that the item is being held by the right person.
The first approach will probably be easier and more-likely-to-succeed, but we'll see what works out better.