Windows 10 Enterprise, 10.0.19042, KiCad 6.0.7. I was modifying a schematic, made required changes and ran the electrical rules check. Among other errors, actually warnings, it reported part not found in library XXX. This part was in one of my libraries stored in c:\users\eid\Documents. I had just placed a part from that library in the schematic. Tried placing another symbol from that library and low and behold none of the symbols I had created were there, maybe 50 or so. However the library was now populated with KiCad library symbols, in particular all the symbols from the Power library. I checked the .bak file and it also had all the power symbols and none of mine. This is the second time this has happened and I have no idea what caused either.
Did you try opening your library using your OS instead of Kicad. The files are sort of readable. They will show you whether the library has been overwritten, or is still there but some path has changed.
Yes and unfortunately it has been written over. Looked at my file contents then KiCad’s file content and they are identical.
And thanks for the welcome.