My most recent missed flight was yesterday. I tend to do the same route and the same flights. Yesterday was a Friday before a bank holiday and I guess I must have booked an earlier flight than usual. However, I turned up at the gate for the normal flight and when my boarding pass was scanned, the machine made a horrid noise and a red light showed. The gate attendant looked at my BP and told me that it was for the previous flight, which had already left. She sounded slightly horrified. I suggested I might be changed onto the flight that was boarding. Still sounding horrified, the gate attendant said that I should have got a new boarding pass and it seemed to trouble her that I didn't appear to care very much. The net result, after a couple of minutes of typing, was that my BP was changed by biro and I was on the flight that I had expected to get all along.