If you were going to steal bitcoins in this manner you'd run them through a number of tumblers. Tumblers are essentially the laundering facility for bitcoins. Lots of coins from various locations come in, put into a pool, and then get sent back out. There's no way to track coins you receive back to a particular transaction. Since 6% of all bitcoins are stolen, more than likely anyone holding bitcoins has a good chance of holding some stolen ones.