Yes, the ECM should retain the codes. They can still be pulled. And, the light will stay off and the car will drive fine until the next episode. Could be today, could be next week, could be next month. The code will at least let us help you figure out what went wrong that one time. Maybe help figure out how to prevent the next episode.
This is pure speculation, but a flashing CEL usually means a major misfire has been detected. One possibility is, with weather starting to turn cooler overnight, that moisture caused the coil packs to leak high voltage, causing the misfire. But, the two attempts to start it was enough to dry up the moisture enough to stop the voltage from escaping. As I said, pure speculation, but if this were the case, you'll have another episode soon, and it will get progressively worse.