I think this is an exploit; apparently the game doesn't check if something is being stolen if it is being transferred between containers, just removed from one.
Any container will work for this. You may want to switch to a lower weight container, such as a sack of grain (100) or the book from the thieves' guild (5). You can also just open the container while it is in your inventory, but there is a possible problem if you become over-encumbered.
weight bug and disappearing chests 
