I fought a Hill Giant. Associated with the corpses was a potion of mana, a staff of the seas, and a steel maul. I picked them up to sell. The steel maul was removed with all of the loaner gear I had equipped when I left the main arena and got my equipment back. (The potion and staff of the seas were there). Since I had a save right before I went to the arena, I could reload. This time I took all the weapons offered into the area fight, even though the light mace is the only one I would be interested in using. This time I was left the maul as well, i.e. I went from having 2 to having 1. This suggests a work-around, always take all the gear you are offered into the fight just in case a corpse shows up which duplicates. But it is still a bug. Also, the fact that the Hunting Bow is never removed, even though you borrowed it, and you can sell it for a tiny bit of cash is likely a bug too. I can send you a save file if you like -- my android tablet is rooted.