From Luke, we learned that Joseph and Mary discovered that the boy Jesus was missing after journeying a whole day on their return from the feast of Passover held in Jerusalem. I always wondered how that could have happened until I read the revelations to Mary of Agreda as recorded in The Mystical City of God. In those days, the separation of men and women among the pilgrims during their return homeward was customary and the children were taken in charge either by the men or the women. So it happened that both Mary and Joseph separately supposed that Jesus was with the other parent. There are more details given in the book. At any rate, I believe that there's always an explanation for what may seem inconsistent or unlikely to happen outwardly in the Gospels. I remember one person rejected Christianity because he didn't see how Jesus could call himself both Son of God and Son of Man at the same time. I believe that all things were clear to the Gospel writers, so there's no reason for them to give extra explanations.