Actually, the correct format for titletext format is:
titleText [format ["%1",(name(thislist select 0))],"PLAIN",1]
if you even wish to use that. That hint format is rather nice if you don't mind the eternal BLING!
Not that the trigger idea would work all the way but it is the easiest solution. Just make it small enough, maybe < 1 radius. There are ways to check who just got more ammo in a group and if that ammo or weapon is the same that was in cargo of a crate, which now should have less of them, you've got your player. Is as complicated as it sounds, perhaps someone with a less twisted mind can solve this