As we all know, the sound signals are to draw our attention to the flags. but in most cases we rely on the sounds and don't look at the flags.
In race 5 when a few boats stopped a lap early when the committie boat was finishing the assymmetric fleet we had only completed 2 of our 3 laps. They had raised a shorten course flag but did not raise our class flag with it meaning that the shorten course did not relate to us. I clarified this with the race officer at the briefing.
The other clue was that the first 2 boats in our fleet had carried on and started a 3rd lap. I couldn't see why they would split the fleet in that way and carried on.