There are various versions of scripture used to translate the Greek word which tries to show the concern expressed by Mary as "greatly distressed" (Interlinear), or having "great anxiety" (NAB), and looking for him "anxiously" (RSV). All of these words convey the concern of any parent over the apparent loss of an only child. In those days of kidnapping and sale into slavery of humans, the anguish would have been doubly evident. We need to remember that Jesus was human; like Mary and Joseph; and therefore they would have experienced human emotions and normal human reactions.
And yet the response of Jesus is puzzling. This puzzlement of both Mary and Joseph is captured in what we call the "fifth Joyful mystery" of the rosary, the "Finding of the Child Jesus in the Temple." Jesus, the boy, was indeed both divine and human; and yet he had to grow, like you and me, in his humanity. As scripture puts it, he returned home to Nazareth with them, and "increased in wisdom, in stature and favour with God and men" (v. 52).
We also need to take special note that Jesus lived under their "authority" (or, was "obedient to them" - NAB) when he returned to Nazareth (v. 51). Jesus spent his spiritual childhood under the total care and protection of Mary and Joseph. What does that say to you and me? Are we ready to live under the authority and protection of Mary and Joseph? Have I ever consecrated myself, and my family, to the Immaculate Heart of Mary?
The obedience of Jesus to his mother Mary, and foster father Joseph, is a virtue that all children need to learn. It also gives a lesson in obedience to all adult Christians, who need to submit their wills to all lawful authority, including the Pope and bishops, provided they are not issuing directives contrary to the demands of moral order.
We know nothing of the so-called "hidden years" of Jesus, from his babyhood until his public life, except for this one important incident when he was 12 years old. Maybe it could be God's will that this revelation on "authority" was more important than any other event during those years, and one which we usually overlook.