Maybe he hid the rest of the coins somewhere else safe and planning to retrieve the coins once he was released 
Maybe he put the private keys for the wallet inside Flashdrive and put it inside bank safes ?
Or maybe he already used the rest of the coins to buy cat food
Maybe he put the private keys for the wallet inside Flashdrive and put it inside bank safes ?
Or maybe he already used the rest of the coins to buy cat food
Hopefully he used a brainwallet with a shitty password, I've always wanted to be a millionaire.