After installing 'Feature update to Windows 10, version 1803' Thunderbird ran but did not find my profile. It ran like it had been installed for the first time. I checked the Users T'bird files and it appeared they were all there, but I didn't look closely. (There were more files and data than after installation of v60.2.1.) So I went to the Mozilla site for T'bird help. An answer to the question "thunderbird corrupt after windows update failure" @ "https://support.mozilla.org/en-US/questions/1220942" suggested uninstalling T'bird and reinstalling it. I assumed uninstalling T'bird would not remove it's profile data. Apparently it did. C:\Users\...\AppData\Local\Thunderbird shows it was newly created when I installed version 60.2.1 which replaced version 55 or so. I do have a backup of the hard drive that's about 2 months old.