I suspect most events like you describe probably would occur too quickly for conventional cameras to capture, but I see your point. It seems to me that kind of mition would have to take the form of a percussive force that arises without visible warning -- like the launch of an explosive powered bullet, and unlike the launch of a golfball being struck by a moving golf club that rapidly approached the stationary ball before making contact. And as you suggest, I doubt the firing of a bullet is the kind of motion seen most often in videos.
I suspect the vast majority of conventional motion sequences follow a path of 1) slow accel followed by slow decel (providing little clue as to directon of time), or 2) slow accel followed by fast decel (something that occurs often in forward moving time sequences, as a moving object is stopped suddenly by an impact). Thus path #2 is probably frequent enough and visible enough to be the anomaly that lets Freeman's group recognize the backward passage of time.