I didn't imply that they left with the coins...  I do believe rather that they did get eaten slowly and surely with transaction malleability.  It's a shame that they didn't had two level of balance verification.  They just assumed that their algorithm worked.  Some transactions happened to not make it through and being "rejected".  Gox assumed that it was just because the transactions got lost, due for example to too little transaction fees, and just re-issued it.

You take all gox transactions, and discard the "failed" ones, and what you were left did balance.  But no check was done in the other way, checking if the sum of users balances did match Gox sum of BTC balances (hot + cold wallets).  So, those "failed" transactions really did pass...  just with different transaction ID, but still eating from Gox wallet.

What will happen now is that even if Gox come back, they will probably have lost the public trust.