I got a puncture from something on my first RAGBRAI. Patched or replaced the tube after carefully checking the hole in the tire for any sharp debris without finding any. It was fine for several weeks but then I got another flat. On inspection it was right over that old hole so I checked again without finding any debris. Near as I could tell and the same conclusion someone above reached, the rough rubber edges of the hole gradually chewed through the inner tube. This time I patched the tube and put a patch on the inside of the tire and no trouble since.
I also kinda got a flat on rollers last winter. Not exactly but one night while filling the tires I managed to bend the stem holding the Presta valve sealer one bend past the point of metal fatigue when I put the filler hose on and of course as I pumped air in the tire the internal part of the valve got blown into the tube and when I took the filler off there was nothing left to seal the valve, hisssssssss