Looks like this could be filed away with today's OP.. Flat Tire , No puncture. Yesterday, I passed by my favorite bike shop and told them my story. The mechanic said that is weird. But, in some instances, take off the tire, turn it inside out and bend the tire so as to cause a crease in the casing. Should any piece of metal be present , it might show itself in the fold. I found two small thorns . But on the outside of the tire, the puncture holes were so small they could not be seen. Maybe I should buy tires with thicker casings. The Tire is a Performance Forte.