Have you tried connecting via your Facebook account? Although you might not remember it, it's not something that chess.com can pluck out of the air.
If you still run into problems, let the Support team know via https://support.chess.com/customer/portal/emails/new
I am not sure if this is the right place to ask, but I am struggling to login to my account in chess.com. I have forgotten my password and when I try to reset It asks me to connect through facebook, which was not the way I signed up the first time. I now had to create a new acoount to post this question here. But would like to go back to my old account, any idea what the issue is. Has anybody else faced this issue. Thanks