Luke 2:46

‘And it came about, after three days, they found him in the temple, sitting in the midst of the teachers, both hearing them, and asking them questions.'

It would take the parents all night, and even some of the next day, to get back to Jerusalem and then they began their search. Nor would they find Him immediately, for they probably went to different places where relatives had been staying to check there. It was thus not until the following day that they found Him in the Temple. He was either completely oblivious of the fact that He would be missed, or having discovered that they had gone, was making the best of it. (His thought would be that after all, if they wanted Him, they would know where He was. To Him it was so obvious that it did not need to be spelled out).

They discovered Him sitting among the Teachers, and listening to their wise words, and asking them questions. He had soon learned to discern which of them had something worth while to say. It was quite normal for great Teachers (and not so great Teachers) to sit in the Temple speaking to their disciples, and whoever else wished to listen.

‘After three days.' That is, not on the day they returned, but the next day. Jesus had seemingly spent at least two nights in the Temple. But it was well lit and He had possibly not noted the passage of time, and He would have been able to snooze whenever He needed to. Furthermore at this feast kindly folk would also have gladly given Him food. It was a time for generosity. He meanwhile clearly assumed that His parents must be quite content as they had not sent for Him.