Thing is, we may not even have heard the scream. If you assume the base DC is about -5 (It's 0 to hear people talking, and -10 for a full-on battle, so a scream is probably somewhere in the middle), and probably a +5 modified since it's in the middle of the rain, and there's a +30 modifier from distance (300 ft up, right?). So that means that the Listen DC is approximately 30. Cade couldn't make that DC even on a 20 (his highest possible score being 28). At best, it'll be about 25.
Whoops, Phaedrus said it could be heard from the ground, nm.