You should file it on your insurance no matter what. They don't expect you to check on your things every single day, or to have receipts for an old item. It will be easy to prove you had the horn (there are pictures somewhere, I'll bet). I do think you'll be able to find it at a pawn shop, too, if that's where it went.

Sucky apartment people! I might consider making them let me out of the lease for their incompetence, even if I didn't want to move.

Karen