I didn't bring this up just to rant but to say that I blame christendom's institutionalized mindset for the (bad) translating tradition of making twelve year old Jesus say, "Didn't you know I had to be in my Father's house?".
Simply put, there is no good reason whatsoever for inserting the word house. "About my Father's business" isn't perfect, but it's infinitely better by comparison. And while it's nice that recent major translations put this in as a footnote, isn't that backwards? Seriously, why should the editorial content go into the text? If they're so set on respecting tradition, couldn't the footnote say, "Traditional rendering: 'in my Father's house'"? But then they'd have to consider the best option - leaving it out completely.
The Greek literaly says, "Didn't you know I had to be in the [things] of my Father?" (OR "in thes of my Father" if English had a plural "the"). But I have a suggestion. Since the article
Not even the Vulgate says "house"!
et ait ad illos quid est quod me quaerebatis nesciebatis quia in his quae Patris mei sunt oportet me esse(My Latin's much worse than my Greek, but I know it doesn't say house! I think the end of it says, "I had to be among these who are my Father's." But if someone could check me on that, I'd be grateful.)
Jesus' question does imply his parents were surprised to find him there, and they could have found him before sunset on the second day, after walking back, if they'd gone straight to the temple. The Temple was the last place they looked. Now, they'd been in Jerusalem together for at least a week and Jesus had chances to go see the Temple, if he'd wanted Joseph to take him. Apparently, Joseph & Mary didn't think he was much of a fan.
BUT, when the festival ended and the crowds started leaving, Jesus made a bee line for the Temple courts. I'm guessing something (or Someone) told Jesus he'd find more devout folks there after the hubub was over. When you think about it, this is all as plain as day. Jesus going to the Temple one day after the festival is like going to First Baptist downtown one week after Easter. There may still be phonies but you're more likely to find real devotion.
After all, there's nothing wrong with having a regular, sacred space. ;-)
But timing can be just as important.