Yes, I know you lost your son tragically. I'm truly sorry you and your family have had to live through such trauma and grief.
One of my brothers was such an escape artist/adventurer when he was around the same age. One day he disappeared from home accompanied by two of our puppies. After the police were called, my mother interrogated and our home turned upside down, they found him playing with the puppies in a teacher's car at my primary school (over a mile away and, yes, he too had to cross a main road).
Not long after, he went missing again. He and his similarly-aged female friend took his pull-along trolley full of returnable soft drink bottles to cash them in at the local shops to buy lollies. On that occasion he crossed the main road and was hit by a car. Luckily, he only sustained a broken leg.