This happened when I was using my computer as normal. I had just installed an app (icloud for windows). All the icons on my desktop and taskbar disappeared, after a restart my user files are all gone (documents, desktop, downloads, etc.) and any apps installed on my C drive are either broken or gone. Can provide more information if necessary, but this reeks of a corrupted user account, right? I can’t understand why it happened out of the blue, though.
So if you browse the c drive with file explorer, your user name is not in C:\Users ?
If you lost the whole profile name then I would question the legitimacy of the app you downloaded. If u do see your user folder then I would question what user id your signing into the computer with? the iCloud app may have added another signin account.
The folder name is still there- it’s just that under that, Documents, Downloads, Desktop, etc, have disappeared and unavailable when trying to access them from quick access.