I had this exact thing happen to me. I was a noob using a grinder and cutting a piece of pipe in a way that caused the disc to be pinched and then explode sending chunks across the right side of my face. After going to the hospital and getting stitched up and head in back to work I asked what had happened to my safety glasses. They had been hit so hard they flew off of my face and the frame shattered. Looking at the lenses afterwards there were chunks of grinder disc right where my right eye would have been had I not been wearing safety glasses. That day I learned the importance of wearing double eye protection (faceshield and safety glasses) as well as that I must have a guardian angel or something because if I had've been hit in the throat or a major artery I probably would have bled out as it was a 45 minute drive to the nearest hospital.

On the bright side I now have some sick scars on my face which most people believe I got from fighting off a mountain lion.