Luke 2:43, 47-50

and when they had fulfilled the days, as they were returning, the boy Jesus tarried behind in Jerusalem; and his parents knew it not

and all that heard him were amazed at his understanding and his answers. And when they saw him, they were astonished; and his mother said unto him, Son, why hast thou thus dealt with us? behold, thy father and I sought thee sorrowing. And he said unto them, How is it that ye sought me? knew ye not that I must be in my Father’s house? And they understood not the saying which he spake unto them.