The domain you listed is still active (as you stated), and thus we won't be able to make any changes without verification. Since you're from the same domain as the other user it would be best to pursue the route of claiming the domain and thus being able to claim any users within your claimed domain, sounds complicated? It's really not that difficult to do.
To proceed forward with claiming your domain and thus gaining access to your abandoned site please review: Verify a domain to manage accounts.
The above will allow you to manage any account associated with your domain once claimed.
For additional information on this, please see Atlassian Organizations & Domain Verification | What is an Atlassian Organization?
Unfortunately, I can't release that information via the Community as it's a public channel. I can say that their first name started with an N and the last name ended with X.
I also cleaned up your reply as it had an email from another user, didn't want that publically available within the Community either.
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