The event isn't hooked. You could use onunacquire instead, though. Or you could give the pc a widget to give the npc whatever it is they want, by targeting the item. I strongly suspect, however, that one or more of the henchman systems on the vault has this sort of thing covered, since I recall playing through SP adventures where hench inventory was nonproblematic, years ago. Hopefully someone on here can be more specific - I don't use henchman functionality at all, myself.
Funky