Autosave

I was working on a very big piece, and i had made many changes, and i accidentally hit 'parts' and then i hit 'open selected' after selecting a part. Realizing this was not were i wanted to be i hit undo. The score then closed and when i reopened it all my work was gone. I checked the like backup section of the files but it was not there. I made it so i could see hidden files and it was not there. I am so sad that all my work is gone and confused how this even happened, like why did the whole score just close. Please help.