#1 - Dec. 12, 2011, 2:34 a.m.
Cancel the auction.
Go to the "completed" auctions tab.
Select the item on the left side of the screen, and hit the sell button in the top left.
Set a buyout.
Now watch as the item is said to have been :
A) Listed as an auction
B) Returned to your "shared stash".
However, I can report that the item will appear in neither of those, and has simply "vanished" into thin air.
By the way, this bug is replicable which is why I am reporting it!