They begin to search Jerusalem and no doubt to go back to all the places where they had been before. It was three days before they found him – probably including the day’s travel before they noticed he was missing, another day to travel back to Jerusalem, and a day searching for him in Jerusalem.
Though we take account of Christ unique combination of natures as the God man, we learn that even a child can make great advance in the understanding of Scripture at a young age. We must all teach our children the Scriptures as soon as they are capable of understanding them.