What do you mean "gone"? Do you mean you are having trouble finding the file you saved? Could be you saved it to a different folder than the one you are looking in. Your OS should provide a facility to help you find files; check that out. If you want our help, we'll need more info - what OS, what folder you think you saved to, whether a crash happened, etc.
Comments
Try finding a backup, see https://musescore.org/en/handbook/file-formats-0#msczcomma and https://musescore.org/en/node/52116
What do you mean "gone"? Do you mean you are having trouble finding the file you saved? Could be you saved it to a different folder than the one you are looking in. Your OS should provide a facility to help you find files; check that out. If you want our help, we'll need more info - what OS, what folder you think you saved to, whether a crash happened, etc.