i am praying that my own "every ride a flat saga" ends today. new tube after sunday's flat. new flat today about 25mi into a 32 mi ride. got the old tube, found the TEENY hole, new tube, hole in same relative spot. inside of tire felt completely smooth to the tip of my finger, but there was a tiny hole on the outside and a tiny dark spot on the inside. fingernail picking revealed a hard spot. tweezer work and out came a miniscule little shard of glass, perhaps 1mm by a half a mm, triangular in shape. my first two flats were different tires, so this little guy can only take credit for half my bad luck this month.
geneg perhaps it's something you can't see, but could feel with your fingernail.