Well the kid isnt just going to have $12000 to deposit, so honestly lets run thru the possibilities.
Borrowed money, is a random person going to loan a 20 year old thousands of $$$ to play poker online? Did the parents give him money? No and no, so its not that...
Deposited the money, ok like I said he cant deposit $12k, so even if he deposited... $5000, losing players generally will not improve the $5000, so even if he made a massive deposit, its at...$12000 now.... so hes obviously winning.
Won the money, so he won his $$$ playing poker because hes a semi-decent amature player, obviously practices BRM and is capable. Most likely a realistic option, so narrowing these options down I conclude it wouldnt be hard for a good parent with a remote margin of brainpower to figure out this blatently obvious situation.