Yes they gather SOME things - but when things are scattered far and wide, land in tall grass or over the side of a ravine, and you are needing to be lifted out fast, they leave a lot of stuff behind. Not everything is found. They arent going to waste time trying to find stuff when the priority is getting you out of there and to a place where the right help is available.

12 years ago I was in a minivan, and was hit by a drunk driver at 70 mph head on - my eyeglasses were found nearly 75 yards down the road...by someone who knew me...a few days later...

Unless the shoes are absolutly knocked off - the shoes go along and I can say from an er nurses perspective that if the person was a runner or a biker we did check shoes!