I'm a big guy at 6 - 2 and 260 lbs. I rode about 850 miles on my OEM tires, then got two rear flats in three days - couldn't find what flatted 'em, pin holes were in the tread side of the tube, and I inspected the tire very carefully for a thorn or glass chip, whatever. I did notice that the rear tire was getting very thin - I could see pinholes of light through the tread area.

I replaced both tires with Schwalbe Marathons ("unplattbar" as the Germans say). No problems since.

Since your bike and tires are new, I'm betting that it was just bad luck to get a flat so soon, but be sure to inspect the inside of the tire while you have the tube out, and make sure that you know if the hole is on the rim side or the tread side of the tube - if on the rim side, it could be a spoke or a problem with the rim tape.