Gutting to see man, but your alive, that's the main thing.
If the speed limit on the road is say 80km/hr... And there are not speed advisory signs for that particular corner, then as the driver you can assume that is it safe to take the corner at the nominated speed limit.
If there was an advisory sign, it is just that, a mere guide at which speed to use.
So I think what the cop said about your speed is just reasoning with no backing.
If you were in the right, make sure your fight this