HTC customer support has even said certain phones do not use Gorilla Glass, including ones listed on Corning's website. Although I don't necessarily believe HTC support either.
I have scratched my digitizer with my finger (not fingernail -- just the pad of my finger that you are supposed to use). I assume something abrasive got on my finger to cause that to happen, although I have no idea what or where it could have come from. The two scratches are right in the path where I normally swipe left or right to switch between home screens. Anyway, it wasn't like I was applying any significant amount of force with my finger so I find it hard to believe this is really Gorilla Glass. Unless somehow I got a microscopic spec of diamond on my finger? :P Either that or Gorilla Glass is not all it's cracked up to be.