Whoever has stolen or hidden these Bitcoins are easy to hide their entire life time as they are protected by the anonymity that the Bitcoin gives. The person right now might be roaming in some beach sipping a juice with the bitcoins safely secured in his/her cold storage.
Well, to a certain degree. If the coins were mixed properly and sent to BTC-e and other exchanges a relatively long time before Gox went belly-up, then people may indeed have been lucky and successful in hiding their identity... Oh and if this was Karpeles, he would be sipping a Frappuccino, of course!