Widad ES-SOUFI

Dear all, I was working on a tex file when suddenly texstudio stopped responding. I had to shut down twice the system. When I finally started it, my tex file was blank, there is actually something in there but it is all void (like space), I tried to select it and paste it in notepad but I got NUL NUL ... NUL as content! How can I recover my tex file knowing that I already activated the save all option, a long time ago. Where exactly are placed the backup files? Because I didn't find any file.bak...