I'd say so

It seems to be a policy of theirs that if it's been over a year, it's gone. They might even have erased the records of it - you can check by going here:
http://www.neopets.com/randomfriend.phtml?user=Add your old username on the end of that. If it says:
This account has been disabled. then the records still exist, but if it says:
Sorry, nobody by this name exists in Neopia.
Then the records have been erased. You could probably create a new account with the same name if it's been erased. In any case, it's probably too late now to get the old one back. Sorry

It says This account has been disabled. But Bryan(a staff member) replied to one of my emails said "this account has been frozen for over a year hasn't it" So it probably is there policy.