so, i was making a score and i placed a note on my whole score disappeared is there any way it can get i back i was working on this for hours please

It sounds like you are saying the program crashed? If so, simply reopen the score from the file you saved. MuseScore also makes an autosave copy to restore any work you did since the last save. So, start MuseScore, use File / Open and navigate to the folder where you saved your score, and you should be good to go.

If you literally worked for hours without saving, first, please understand that saving is always your responsibility - not just in MsueScore, but pretty much all computer programs. But even so, depending on what OS you are on and whether you've tried creating any other new scores since this (if you haven't yet, don'!), it might be possible to recover the autosave. So if that's the case, let us know which OS and also which version of MuseScore, and we can try to assist.