Automatic Transmission Park/neutral Start Switch problems of the 2004 Honda CR-V

My car had been parked for several hours at a relatively flat area at the top of a hill. When I got in to start the car, the light came on that the tail gate was open. I went to the back of the vehicle to slam the gate and the window. When I got around to the front door of the car and opened it, I heard a pop and the car started rolling. I stuck my foot in to get my foot on the brake, but the open door knocked me down and the car continued rolling till it hit a stone wall. I am sure that I had the car in park. That day I got a rental car which has the gear shift on the floor. My car has the gear shift on the dash board. For days, every time I stopped, my hand would automatically go up to the dash board to move it into park. I am sure I had the car in park. It was not rolling when I was standing behind it to slam the tail gate and window. It was not rolling when I went back to the front door. I don't know what the "pop" was, but that was when the car started rolling. Fortunately, my injury was slight. When the door knocked me down, I rolled away from the car. The bottom of the open door bruised and gouged the front of my right leg. I did not go to the hospital.