What NPC did you trade to? Did you talk to the same NPC when you wanted to receive the armour? What did you trade them? You definitely don't have whatever Hunter's item in your inventory any more?

If this truly has happened then your best bet would probably be to make a bug report here in the bug report part of the forums, and of course use the proper bug report format or you'll get nowhere.

First I would contact a GM to make sure there is nothing they can do to help but they may just advise you to make a bug report.