It's just like what bertsirkin described. I actually couldn't believe that one of them was halfway sticking out!

The only reason I discovered the missing bolts was that when I was washing the front bumper right in front of the left wheel, I found that I could pull the bumper off slightly with a gentle tug.

I looked under and spotted the hole at the end of the bumper with the bolt missing. When I looked under more carefully, that's when I saw the other holes (starting from the center) where the missing bolts were supposed to be!

You need to really lay on your back and look up to check the bolts or use a mirror.