Have no experience in this, but the opposite. I guess I had a different old account when I was a kid, and while it had 0 new miles or anything redeemable, it did exist and it has since been merged with my newer (still old) one. Useless merge unless I ever get close to a million miles, but still.

All I can say is are you 100000 percent sure your account number (and zero versus "oh") is correct? Do you have some marketing emails or account statements with that number listed you can forward them? I see you indeed say you do, were they willing to receive any of them as a forward? I've heard of miles expiring, and entire accounts, but not with AA...