Visualboy Advance Pok Why Did My Visualboy Advance Completely Erase After I Beat The Game?

Why did my Visualboy Advance completely erase after I beat the game? - visualboy advance pok

I had a game in expectation of my Visualboy beat and then left because he said: "SAVING Do not Turn Off the" power and then I started again because he wanted to wait for the credits, then he said that the file saved was deleted due to corruption or damage. What can I do to fix it, because I am beginning again.