After last night's change to skill points, a few players had items in their bag that did nothing when used, for example a Yellow Potion. It happened when a character still had a skill book in its bag at its first login after the change: the book was exchanged for its price, and until the next login the places in the bag were shifted by one.
This is fixed since this morning's short maintenance. Logging in again already put a bag right. If you think you sold or dropped the wrong item because of this, please send a bug report from the game and name the item.