What probably happened is that the person who had your account changed your WLID. So now, when you signed into it on this website, it actually created NEW gamertag for you. What you need to do is check the email(s) you were sent at then end of your investigation. Typically the investigation team changes the WLID on your account from the one that the theif changed it to. It's usually SR1161email@example.com (it will be the case number of your investigation) THIS is the email that you need to sign in to to recover your gamertag. Please refer to the email(s) you were sent at then end of your investigation. Good luck!