Breaking Up the Shackles

Four friends are on a night out to celebrate the arrival of a brand new car that one of them gets as a gift from his father. In the midnight they stop their car near the only roadside smoke shop on the entire highway. Two of them get off to buy some wine and weed. They return to find one of their friends lying unconscious in a pool of blood. The fourth one is missing from the car.Where did he miraculously vanish just within ten minutes in the darkness of the citys outskirts? Did he hit his friend and run away or was there something else other than these boys and the shopkeeper?