Not sure if this counts, but in Pokemon Ruby, I had entered the E4's door on accident. I tried to leave and couldn't so I decided to just turn off and on. I couldn't remember when I had last saved though...but then my brother stole my DSLite and tried to save my game. He pressed the save button, it began saving...he dropped my DS and the game froze while saving. I was so mad at him because I had a shiny on that file!
Anyways, after being incredibly upset and scared, after a day or so I decided to see if my save was still there...I turned the DSLite on and the save was corrupted. I pressed A, shaking, and it sent me back to where I had last saved: grinding in Victory Road. All my pokemon were weaker and had lost a few levels, but I didn't care! At least the save was functional!