His mother treasured all these things in her heart

In this Sunday's reading from Luke 2:41-52, the twelve year old Jesus gets left behind in Jerusalem by his earthly family. 

Now every year his parents went to Jerusalem for the festival of the Passover. And when he was twelve years old, they went up as usual for the festival. When the festival was ended and they started to return, the boy Jesus stayed behind in Jerusalem, but his parents did not know it. Assuming that he was in the group of travelers, they went a day’s journey. Then they started to look for him among their relatives and friends. When they did not find him, they returned to Jerusalem to search for him. After three days they found him in the temple, sitting among the teachers, listening to them and asking them questions. And all who heard him were amazed at his understanding and his answers. When his parents saw him they were astonished; and his mother said to him, ‘Child, why have you treated us like this? Look, your father and I have been searching for you in great anxiety.’ He said to them, ‘Why were you searching for me? Did you not know that I must be in my Father’s house?’ But they did not understand what he said to them. Then he went down with them and came to Nazareth, and was obedient to them. His mother treasured all these things in her heart.

 I have to wonder if this story was passed on to Luke by Mary herself or a close friend of hers. Mary treasured this event in her heart and probably did not dare talk to others about it in Nazareth as it would have been gossip material for her neighbors and could have made teenage life difficult for her son.