The cap might not been initially tight enough since the message eventually went away after tightening it. In my 99 Accord I had, I filled up, thought I had it tight enough. The (check engine) light didn't come on right away, but when it eventually did I was going crazy trying to figure out what was wrong. I was at around 103,000 ... so I was thinking O2 sensors among other things. Read the maual, tightened the cap and it took three full cold to full warm drives to make the light go out. I think your car was just notifying you that the cap wasn't 'perfectly' secure, and it is an emissions saavy car. You might have had it almost to a click, and then through some vibrations (RR crossings, potholes, rough road surface) it loosened slightly and that would cause the delayed reaction. You could always do an experiment and loosen the cap start the car, then tighten it and see if you get the same pattern.

That is a nice feature to TELL you what is wrong. Does anyone know if the HCH I does this as well, since it is also a matrix display?