Laying on their stomach is a BAD idea. When you have your first positional asphyxia arrest you'll change your mind. Having been there, done that, I assure you, it sucks. Don't transport restrained patients prone.
In five minutes I had not only his name, but his DOB, last known address, a short medical history and enough information to determine his fitness to decline treatment. I made him promise to stay far enough off the road to avoid getting hit. To stay safe and in the future, to move further off the highway if he needed to take a nap. He shook my hand, thanked me and went on his way.
The big difference was instead of demanding his name, I put my hand out and introduced myself.. My name is.. and what's yours? Instead of an interrogation, it was a social exchange.
While I would be the first to put my boot in a butt, and roust an "unconscious" drunk from a park bench, the corner booth at KFC, or under the boardwalk, rather then take them to the hospital if they don't want to go, a highway is not the place to place boot to butt, and take his word that he will stay off the highway.
Do something that is completely out of the ordinary (try to nap on the casino floor), or that completely contradicts something I request ("please sign here, and move on sir", and I end up with a short narriative of his lifes experiences in Vietnam), and you go.
I won't take the chance of them doing something stupid again, and have it come back to bite me in the arse.