Brakes - Possible Hub or Lost Brake Pin?

I don't know what else it could be besides a stuck brake. I got in my car today(after 3 days of driving in the rain- if it helps), I stop at two lights and I hear what sounds like a plane overhead. I pull into a parking lot when I could and see a lot of fresh brake dust on my right back rim(black, dusty, not caked or brown). When I drive the brake isn't rubbing and creating that sound unless my car is leaning to that side or if I hit a bump, but once I put my foot on the brake it crunches down even on a light touch of the brake. I went to the dealer last year and got all new brakes(4) and there is no brake dust on the left back side or any other rims. I have asked for some help from friends, them telling me its the wheel hub or a lost brake pin. I will get the dealer to fix if I can not. Please Help :)