Well he should have swapped it on a different IP/Proxy so he could claim his account was hacked and then say the GT was changed, but then after calling they'll ask you if you had a CC on the account and if you say no they'll most likely tell you to make a new xbox account. And even if that worked, they will just get you your account back, and theres a very small chance you might get your original GT. I have never seen accounts getting reset to their original owner, but I know its possible.