don't you have to put your current address down to HTC when signing up? (Been 7 years, dont quite remember)
If you do, and you have proof that he really did rip you off, have your local police give HTC a call.
They could do anything from get his address from his fill out sheet for the game, Or maybe even track his I.P address the next time he logged onto the game.
I say this because i had a friend last year who had his ps3 stolen from him. He knew who it was because he had caught the person in the act, but they ran off before he could stop them.
Cops got ahold of the kids parents, they lied and made an allebi for him.
My friend gave up hope of retrieving his ps3 so he decided to buy a new one. He had his PSN account set to auto-sign on whenever the ps3 turns on.
One day he was on his new ps3, and a msg poped up informing him that someone else had signed into his ps3 at another location.
He got ahold of his local police who called the SCEA up. i think they tracked the location of his ps3 threw his psn account, because they ended up getting it back and catching it in the other kids possession.
May be able to do that with HTC.