What happened to my account and all of my work?

I created an account.
I started following the course to learn how to code in JavaScript.
I completed about 35% of the course and then…
The page just…disappeared I guess and was replaced with just a white background with an image that was 5 black, vertical lines that were pulsating. Nothing I tried could restore the page I was working on. I even shut down and restarted my computer. I was able to find a login page, but when I entered my username and password, I got an error message that said my no account or email address existed, like my account (and all the work I had done up to that point) has been deleted.

What happened? And what can be done to restore all the work I had done to achieve the JavaScript certificate?!