[Scott Douglas]

My wife had that happen to her car, before she was my wife.
Some kids put small rocks under the valve stem caps to slowly bleed the air out.

I had a 3/8" diameter x 2.5" long sheet metal bolt give me a flat way back when I was working.
I remember driving to work at @5:30AM and it's still dark out. Taking the 405 N to 105 W exit I ran over something going around the 'Nascar' turn as I called it.

This was in my BMW 325e.

I heard a loud 'FWAP' on the right side as the lanes went down to only one lane.
I parked in my usual parking spot in the parking garage and looked at the rocker panel on the passenger side. Found a large black mark that looked like it came from a piece of tire rubber.

Didn't think much of it and went on in to work.

Came out to go home and find I have a totally flat front tire on the passenger side.

I changed the tire and was glad I'd checked the air in the spare.

Got the tire off and found the bolt firmly embedded in the tread, right smack dab in the middle.
Tire shop put a plug in it and I had them put a patch over the plug on the inside just to do the 'belts and suspenders' type repair I used to do when working at the gas station.

Tire took a little more weight than usual to balance it after that but it was good for many more miles of commuting.

Only thing I could think of was that bolt must have been used to hold a mud flap on and it'd fallen off.

I used to carry that bolt around in my tool box that I kept in the car as a reminder of how lucky I was that morning that the tire didn't go flat instantly. I might not be here today to tell the story if it had.