I had the same thing happen to one of my company cars about 10 years back. I was on a big open highway with nobody remotely around me and a rock cracked my windshield. I had no idea how that could happen until the owner of the glass shop told me how you can fling a rock out of your own tire. I had never heard it of it before then. At first I was thinking maybe a kid with a pellet gun had shot the windshield.
Luckily mine was just a chip, but when it happened, I wasn't even upset, but curious what the odds were of that. Maybe we should go to Vegas.
If its jut a chip that has no chance in turning into a spreading crack, I just leave them be. Not worth the time to fix a chip each time it happens.