Dungeon loot from boss chest not able to be traded

Doing The Oculus random dungeon today and at the very end a player asked if I needed the Ancient Dragon Spirit Cape I received from the loot chest from beating the final boss. I tried to trade the item and it was not able to be traded. I checked and an item I received earlier in the dungeon from another boss, looted from a corpse, was able to be traded to that same player.