Children wandering away from parents in public places is so common as to be a stereotype, and we would hardly be surprised if parents express concern. At the age Jesus is portrayed, young boys were expected to show themselves able and willing to cut the apron strings, so to speak.

Some question whether Mary and Joseph were irresponsible for losing Jesus, and why they did not understand his response about being about his Father's business.

First, Mary and Joseph sought for Jesus 'among their kinsfolk and acquaintance.' This was a family traveling group, and young pilgrims like the 12-year-old Jesus were considered safe as long as they were in the company as a whole. This is in line with the extended-family concept of the ancient world. On such journeys, parents might not see their sons for hours at a time. Jesus must have been with the group as it left Jerusalem and detached himself shortly after they started their journey.

Regarding their lack of understanding: What they did not understand specifically was 'the saying'—what Jesus meant by 'his Father's business' and how it connected to finding him teaching in the Temple. In the birth narratives, they were told Jesus was conceived of the Holy Spirit, would save people from their sins, and would have the throne of David. There were no specific details about a mission involving teaching in the Temple. Messianic expectations at the time ranged widely, and being a teacher sitting in the Temple among the rabbis was not a typical aspect of the Messianic paradigm.