The above article may help, but it's possible there is something else going on. Can you explain your issue in greater detail? If you deleted a file from your drive, normally you can simply go to the recycle bin or trash or whatever your OS calls it and retrieve the file that way. MuseScore itself never ever deletes your files, so the only way it could be deleted is if you deleted it. But, it could be you simply forgot which folder you saved it to.
If you never saved it, then of course, your options are limited.
Comments
See How to recover a backup copy of a score
The above article may help, but it's possible there is something else going on. Can you explain your issue in greater detail? If you deleted a file from your drive, normally you can simply go to the recycle bin or trash or whatever your OS calls it and retrieve the file that way. MuseScore itself never ever deletes your files, so the only way it could be deleted is if you deleted it. But, it could be you simply forgot which folder you saved it to.
If you never saved it, then of course, your options are limited.