That's scary. Could you quit/exit Thunderbird and try starting up in its Profile Manager to see whether you are using a new (empty) profile and can switch back to your regular one:

Using Multiple Profiles

Important: never remove any profiles in the Profile Manager without making a full backup because it's far too easy to accidentally remove the wrong one.

I'm running mint Linux, not windows.

If this site's help articles do not show Linux-specific instructions, expand the "Editing Tools" section in the left column and use the Customize drop-downs to match your Thunderbird version and operating system. Then a script in the page should switch to the steps to use terminal to run the Thunderbird profile manager.

Sorry- I missed the Terminal instructions at the tp of the article. I only used the "Default" profile and it appears to be gone, at least the version I was using.

Hopefully not gone but perhaps missing from the profiles list for some reason. If you use the location information in the following article to look for the profile folder on disk, can you find one with file modification dates/times closer to when Thunderbird was working normally?

Profiles - Where Thunderbird stores your messages and other user data

It looks like that would be in

~/.mozilla/Thunderbird/

But as a Windows person, I'm not able to confirm that myself.