Nve, when you get to point 3, originally stated in your post as:
"Vet and could not find a microchip" which you claim contains no conjecture. I disagree, you have assumed this means no microchip. Perhaps erroneously?, but with this added information:
"Vets scanner sits on a docking station so the battery can not go flat" it seems far less likely of a microchip being in situ.
Im lovin that the dog is being returned to his owners relatively intact, considering what could of happened.
And if my dog gets run over, id like a Nev on hand to help him out any day.