I went to unequip an item (Hawlic's Armor) in the ogranization step before an adventure and afterward it has completely disappeared from my single player collection. If I remember right, I dragged it from an inactive character and dropped it on a party member. It doesn't appear when searching, switching the filtering between all items and heavy armor, or any other way of finding it that I could think of. However, I can still find it when I go to edit my multiplayer party. Update: It came back after I restarted the game. That was rather odd.