I created a gmail account in 2004 and then completely forgot about it. Just last week I realized that I had registered that account. I went to the forgot my password page, and it prompted for the last password I remembered using, which I took a guess at. It told me that wasn't enough information to recover the account, and that was it, because I didn't have a backup phone, email etc. attached.

But then I thought- what if I just try that password to login. And it worked.

So when I thought I had forgotten my password, gmail prompted me for a piece of information that I got correct, and then wouldn't accept it.

I also have another email account that forwards all mail to my main account, but I've definitely forgotten that password, and I have no way to actually get back into that account, even though I've tried. I guess it just forwards mail forever.