Gamertag showing up as does not exist

I was invited to Preview, but my gamertag showed up as nonexistant when i was invited.

:)

 

Gamertag does not exist

Hi there,

gamertags are unique across several services, one is the xbox live service, but there is aslo the Zune service.

So your gamertag may be in use on one of those other services, that's why it mentiones that it is already in use and why it is saying that the gamertag isn't existing on xbox live.

I don't think there is anything you can do to get it back.

 

Gamertag does not exist

So, I miss my old gamertag and i would like to change it back. The problem is that it says "this gamertag is already in use". I've searched to see if it was and when I went to add as friend it said "the gamertag does not exist". When i had the gamertag,
i also had a different email, but for some reason microsoft made me change it. After i changed the email, i changed my gamertag a couple weeks later. Im wondering if this is the reason I cant change it back. I still do have access to the old email account.
Is there anything i can do to get my old gamertag back?