How to recover GT4 save data after corruption?

1,657
North Korea
With Kim Jong Un
I accidentally turned off my PS2 tonight when the red save icon was still on the screen and now whenever I boot up GT4 the dreaded message appears. I only have one memory card and it still contains my game data, photo data, and replay data on it. Unfortunately, I only backed up my save once at a friend's house 3 years ago and I haven't spoke to him in a long time. I really don't want to restart the game from scratch as I'm already 50.7% through the game and I still want to continue playing on this save.