Wasn't there snow on the ground? Is I fall down in the snow there is not dirt on my clothes but snow which just melts and leaves a wet spot that dries. Only if he falls in an area where there is loose ground or mud will it adhere to the cloths and stay there when dry. So where did his clothes come into contact with dirt? And won't the FBI labs be able to tell by matching exactly where that location was?
Yes the FBI should be able to match what was on his jacket and/or pants, if he still had the jacket on after switching to the sweatshirt. I do wonder what he had in the briefcase and how important it was?
TPTB may be very concerned, also if it was a hit I bet they know that already too. Bet there’s a lot of scurrying going on behind the scenes and a gag on any news going out.