MSCZ_SAVING File name

Have you deleted your automatic backups?

The developers will want to have the score file. Without it they can't see what bug might have caused the trouble.

When MuseScore saves a file, it first writes the content to a mscz_saving file. When the content is fully written to that file, that file is automatically renamed to a normal mscz file which can be opened.

The reason for this is the following: in the unexpected event that MuseScore crashes while saving, the saved file will be incomplete and therefore unusable. If we would save directly to the mscz file, and MuseScore crashes, your file is completely lost: both the version before your changes (because that has been overwritten) and the version after your changes (because that was incomplete because MuseScore crashed).
So, you can see it as an extra safety measure; only when we are sure that the file has been written completely, we overwrite the file that was on disk before saving.

If you have a mscz_saving file and a mscz file, that can mean two things:
- either MuseScore crashed while saving, so the mscz_saving file is incomplete and useless, so your latest changes are lost but the version before that is still safely on disk;
- or MuseScore simply failed to remove the mscz_saving file but the saving did succeed for the rest, so the mscz file should have everything.

But you say that you have only a mscz_saving file. That is a strange situation. You could try to rename it from mscz_saving to mscz manually (assuming you're using Windows: note that you will need to turn on file extensions in Windows Explorer, see https://www.howtogeek.com/205086/beginner-how-to-make-windows-show-file…). If that works and opens fine, then MuseScore only failed to rename the file, but for the rest it worked. Make sure that MuseScore has permission to write files in the folder where you're saving the score.