They found him in the Temple

Every year the parents of Jesus used to go to Jerusalem for the feast of the Passover. When he was twelve years old, they went up for the feast as usual. When they were on their way home after the feast, the boy Jesus stayed behind in Jerusalem without his parents knowing it. They assumed he was with the caravan, and it was only after a day’s journey that they went to look for him among their relations and acquaintances. When they failed to find him they went back to Jerusalem looking for him everywhere.

  Three days later, they found him in the Temple, sitting among the doctors, listening to them, and asking them questions; and all those who heard him were astounded at his intelligence and his replies. They were overcome when they saw him, and his mother said to him, ‘My child, why have you done this to us? See how worried your father and I have been, looking for you.’
  ‘Why were you looking for me?’ he replied. ‘Did you not know that I must be busy with my Father’s affairs?’ But they did not understand what he meant.
 He then went down with them and came to Nazareth and lived under their authority.
 His mother stored up all these things in her heart. And Jesus increased in wisdom, in stature, and in favour with God and men.
(Lk 2:41-52)