I cursed myself...5-6 miles of my main commute was recently chip sealed.
I rode home in the rain Thursday and the back tire felt squirrelly, I assumed it was the wet roads. Went out today to get the bike cleaned up and replace the bar tape. Back tire was flat. Pulled the tube and found the hole after a few minutes and some soapy water.
I Found a piece of flat gravel and a small piece of flat copper 1/2-3/4" or so from a deep cut in the tire between the tread and the kevlar belt. The metal had made it all the way to the edge of the kevlar belt and thru the case on the tire and nicked the tube.
2200 miles and one flat on a rear tire, guess I can live with that. Still hurts to pay as much for a bike tire as a car tire.