Backpack

I just don't get it.

Last night we got home at about 4:30. All the kids came inside with their stuff from their assorted activities, and took it all to their rooms.

But this morning he can't find his backpack.

Is it on your top bunk? no Is it in your closet? nope How about the bathroom? nada Still in the car? still no Looked under the bed? not there either

Any other week, we would probably survive. But he is at day camp this week, so he needs a lot of "stuff" - like sunscreen and aquasox - that we only have one of each and are pretty inconvenient or expensive to replace. But I still don't get it, can someone tell me...

How did he manage to lose the backpack in less than 18 hours?