Update: The admins have decided not to restore my original hijacked account because they feel there is not enough evidence to do so. Oh well. I gave it a shot.
So sorry about the bad outcome, but what exactly did they say?
I believe you used your original email address to send them a message? That would partly be some useful evidence that you are the original owner of the account, and maybe your IP address logs from the previous years.
I still feel you shouldn't give up that easily,
this guy did not, and he got his account back. Maybe make a case about this in Meta board as well.
Yes, I sent them the email from the email address that the account was originally opened with. However, I don't know what it was changed to after the account was hijacked, so who knows what the current registered address is. This was their response to me:
"Unfortunately since the account has no relevant history that could help us with the recovery process, we have decided that it will remain locked. If you want to continue using our platform, our suggestion is to create a new account using a different email address as it will have the exact same privileges as this one. Thank you for your understanding."