DS has always had a hard time paying attention to things that do not interest him. And, frankly, where a lunchbox is just isn't very interesting.
We have lost tons of stuff including a brand new $80 coat. Now DS wears only a sweatshirt because we are not buying him another coat. We gave him the option of going to a second-hand store so he could buy a replacement with his own money, but he decided to just be cold. This has been a painful lesson, but one I think he is learning, very gradually.
I will say that his organization has gotten much better with puberty. I believe that the exectutive function portion of the brain does go through a spurt around 12-13. So we are optimisitic. OTOH, DH does have ADD which was not diagnosed until adulthood. DS has not been diagnosed or treated for ADD, but we still keep the possibility on our radar.