Your files are not gone. They have simply been moved. To check, do this. Go to "This PC". The click Windows. Next, select users. There should be a TEMP profile in there. If there is, that is the account you are currently using. Here is what you want to do.
- Make a new profile with admin privileges.
- Move all the files from your old account to the new one.
- After that, log out and log into the new profile.
- Your files should be there.
NOTE; DO NOT MOVE YOUR FILES INTO THE TEMP PROFILE. IT WILL DELETE YOUR FILES AFTER YOU LOG OUT OR SHUT DOWN.
If you have any questions, reply back.
I have done at least 20 of the 1809 upgrades, both on my own computers and on those of others. I have had no occurrence of this problem. I think that the solution posted by CWWindows10 looks like it is worth a close look and try. Also, there is a comprehensive solution posted at https://www.techbout.com/fix-corrupt-user-profile-windows-10-9139/ posted by Waseem Patwegar that looks sound. Apparently, at least some people have found their missing files and folders in a newly created and hidden Admin identity. As noted in the Patwegar article, "Users have also reported a corrupt user profile after upgrading to Windows 10 from an older version of Windows." That corrupted user file has accounted for the missing files in some cases. I hope that the link gets posted in this reply. If it doesn't, just search on "techbout fix corrupt user profile windows 10" and you should be able to find it. Good luck to all.