Arguing where the first shot hit the road is like arguing about how many angels fit on the head of a pin. The first shot struck JFK, according to the evidence.
Also, the MythBusters video shows that a 1200 fps 115 grain jacketed bullet from a handgun is not going to hit asphalt without leaving a trace. So it is obvious that a 2000 fp 170 grain jacketed bullet, with more than four times the energy of the Mythbuster's bullet, will leave a noticeable divot in the pavement. Does anyone seriously think the FBI could not find such a mark in the pavement if it really existed?