Missed a step?

We were on a bus with our neighbors and they were getting off the bus a few stops before where we were going. As he stepped down from the upper back part of the bus (the part where Ethan normally wants to ride), the bus lurched forward to come to a quick stop, and Jonathan's foot caught the edge of the step, and the step came out of its spot to where we could see the ground below. Doug & I were sitting on either side of the step, and were certainly in shock as we peered down through the bus floor! Jonathan was OK, Doug has a scrape down his leg, and we're all just thankful neither of the boys took the fall like that!