Got someone else's hat?

When picking up presents, for some reason I picked up the Jester's Cap that is customised for someone else.
Not sure how this is possible (you cannot drop things in town, inventory full?), but now I want to give it back and the owner seems AFK.
I know IGN (surprice) and guild, but don't know any other way to contact to her (him?).
And I won't be online that much the next few day's, I think.

Anyone have any surgestion how to give it back (I cannot drop it in town and leave it there)?
And what's a reasonable time to get it out of my inventory, in case I am not able to contact the owner?

This happened to me in the Halloween event. The person was standing right by the hat and wouldn't respond to anything. I waited there for awhile and then all of a sudden i see her put the same hat on so i guess the person duplicated it and then dropped it somehow!?. So I just put it in the trashcan and went about my business.

The person's inventory was full when Grenth gave out caps, and the cap fell to the ground. This happened frequently during the Halloween event.