Trigger here, I found a solution:

I accepted that I wished to create a new record in Thunderbird using my current email address and password. In doing so a very old list of folders appeared along with many old emails. I then left clicked on the Hamburger on this new file, hovered over Help, left clicked Troubleshooting Information, found Profile Folder, left clicked on Open Folder, right clicked prefs, found Properties and left clicked on it, left clicked Previous Versions, left click on the most recent one recorded a couple of hours before my complete email files/folders disappeared. I clicked Restore, Restore and OK. I then went to Ctrl/Alt/Del opened Task Manager, highlight Thunderbird and click End Task to closed the running Thunderbird. On restarting Thunderbird all my current email folders/files are there plus a bunch of copies (I will worry about clean-up later) plus emails that arrived while my Thunderbird was down. I declare my problem solved.

I believe I caused my problem by running Ccleaner since my loss of all my Thunderbird files just happened again to me immediately after running Ccleaner.

Hope this helps Trigger

Good info. Thanks for sharing.