We usually still save the comment in your browser local storage. So it being gone is a bit surprising. I can look into it and see whether I can reproduce it (though it’s also plausible you had some settings activated that prevented localstorage from working, like incognito mode on some browsers).
I think I was on Brave browser, which may store less locally, so it’s possible that was a contributor.
Ah, yeah, that’s definitely a browser I haven’t tested very much, and it would make sense for it to store less. Really sorry for that experience!