Unfortunately in this case, where ever the glass was, I don't recall seeing anything. I rode into the North Abyss I remember feeling like the back tire had compressed a bit much when I crossed a root, but didn't really think about it. I came out of there and headed right into the South. After I had passed the bench, I was feeling like it was a little soft, and as I climbed out just before "big drop" I knew I had to check it.
So it could have been anywhere on the trail. What really sucked is that I was low on Stan's Fluid, so the puncture wasn't sealing. 6 CO2 cartridges later and a half mile walk, I was back at the car.