This has happened twice since I updated (and got the pets and other great new items.)
I got coins for the things that were sold, but I did not drag them outside the gate.

The first time this happened the store screen had just closed, the "Decorate" tab was open because I had purchased a rug and I touched the wide cabinet. Poof! I got the message sold for xxx coins and it was gone. I didn't move it outside the gate, didn't even move it in the room, I just selected it and it was gone.

The second time this happened I was rearranging furniture in the blue bedroom. I selected the doll it vanished and I got the message that I had sold it.

I am playing on an iPad2 and just updated it. (I am loving the new pets, toys and other items, but I am nervous about rearranging things now.)