Go
HERE On the sidebar, go to "How to..." then... "Account Settings" then... "I forgot my email address on the account. Can you tell me what it is?" then... Click on the "Contact Us" link in the paragraph and fill out the ticket.
In the ticket..
Subject: General Account Inquiry
Topics: Account Status
Sub Topics: Can't Access External Email Linked to Gaia Account
Then fill out as much as you can, with as much detail as you can... It asks for your email address, but perhaps in that box just write "I don't remember" or "see description of inquiry" or write in an email that you THINK might be on file...
It might take a while (possibly weeks), but you
might be able to get it back. Someone actually reads these tickets, so it doesn't just go through a computer and perhaps if you provide enough information, the person might believe its really you and give you your password.