After a talking about it (the first time) he claimed he had no idea who did the withdraw.
More about the story:
Now, as I thought the wallet security was compromised, I decided to create a new wallet and transfer the remaining funds to it. Couple of hours after giving the owner access to the new wallet, a new withdraw occurred which , this time, left the wallet empty. At this time, I paused the game and sent some questions to the owner on discord asking what was that as well as letting the chat on winxrp know what was happening.
He claimed this withdraw was to "test the accessibility" of the wallet. 3 days later (today) He still haven't put back the money in the wallet.
According to what the owner told me, he is supposed to put back the money today (2018-01-05) in the wallet.
I think a little more than 15k. Not counting the amount he owed Dexon or other various pplz. Dexon would know exactly, but more or less 15k XRP @$3 each