Was it a gold or silver account, and did he ever connect online?
If he did use it online, the achievements and friends will still be on the MS server and there is a
recover lost GT facility.
But he will need to know the linked email and password.
If you go to xbox.com, there should be a way to reset the password if he knows the email and GT - it will be the email account that gets 'spam' from XBox Live.
Of course if it never went online, then it is lost