You shared almost no information. Is this Windows? Did you check c:\program files or c:\program files(x86) for Mozilla or Thunderbird? Have you looked at c:\users\<yourid>\appdata\roaming to see if there is a Thunderbird folder? Tell us what you discover and we can move from there. If it helps, there is a beautiful little FREE utility named 'Everything' at https://www.voidtools.com/ download that and run it and enter thunderbird.exe and, if it's on the computer, this little jewel will find it within 2 seconds. I use this tool regularly to find what I think are missing files.