It has been a difficulty for me. Aside from the spiritual meaning of loss of Christ Child, there are some hard to digest things from the human point of view:
1-we are taught that a parent must know exactly where his/her child is, when he will return etc.
2-and that childern must inform parents before going anywhere. (ok it this case it was God's will that He stay in Jerusalem)
3-and that you must not depend on your guess or hope "he might be there" when in doubt about where your child maybe.
But our Lady and Her husband seem to be very easy going, not deciding beforehand whether The Child was going to accompany His mother or St. Joseph. They also thought He might be with other passengers. I thought that every child has to inform his parents if he wants to go and accompany other passengers in any trip, but the fact that they thought Him to be with others makes me think that it was not a must for Jesus to do so, otherwise His parent wouldn't make such a guess.
So my conclusion is: either our standards of good and responsible child bringing are wrong, or at those times everybody took parenthood much easier.
What do you think?