Load error

I saved a music file (said file is attached) at 3:00pm today, went to open it 8pm and it came up with Load Error: Cannot read file C:/Users/User/Desktop/Loss.mscz:
The thing is I need this file by Wednesday next week as it is a school assessment piece and my music teacher spent over an hour working on it and fixing mistakes. I don't want to have to tell my teacher that that was for nothing.
If there is a fix for this issue as I said I need the file back Wednesday latest.