I am not a hunter, but from every thing I hear accidents are not unheard of. When I was a kid my brother was shooting at targets with his pellet gun. I rounded the house to see what he was doing and blam, right in the rib cage. I still have the scar and never let him forget the day he "shot me." :0)
It could be that they were not allowed at first, but then were granted access - or Cheney simply gave them a written statement - see links above.
Getting sprayed with pellets when hunting quail is pretty much on the same level as getting snagged with a hook while fly fishing, it's just something that happens. As long as you don't get hit in the eyes the main thing is to get all the pellets out to avoid infection, the people who I've known that its happened to say that it doesn't hurt much more than getting hit with a tennis ball.