Lost work: Cannot Read File

What OS (operating system)?
What version of MuseScore?
Did you experience a system or a program crash?

See:
https://musescore.org/en/node/52116

This seems to be a rare problem that occurs for no reason anyone has ever been able to figure out. but as far as I know you're the first person to whom it's ever happened to more than once, much less five times in a week! So, first, I'm sorry for your loss, but the good news here is, maybe you are in q unique position to finally help us figure out what triggers this - what specific action you did those five times that you don't normally do that somehow might have triggered the bug.

Meanwhile, you don't say what OPS you are on, but msot provide ways of recovering older versions of a score, like from the last save. Windows, for instance, does this via OneDrive. If for some reaosn you've disabled that, this would be a good time to re-enable it, but also, the link shown above should get you to the version that was saved at the conclusion of the next to last editing session, which may help.

That isn't a score file but a PDF with a wrong file extension. I just renamed it, check the attached.
As per the PDF's properties it got cteated fir MuseScore File > Print function and the Mícrosoft Print to PDF driver.
Don't ever use that, use File > Export > PDF instead