I think some of it is normal 7 year old behavior and some of it is giftie behavior or some of it could be slow/lack of develelopment of executive functioning skills. My DS7 has lost (although they were found) 2 water bottles, forgotten to turn a few things in and has forgotten his homework folder.

My DS attends a HG school and when I emailed the teacher about his homework folder she said not to worry she had a lot of folders left behind and that she was starting to remember why she went to packets once a week last year with her gifted kids. I am not too worried at this point as I do see that he is improving on this as he gets older. And with some procedures in place, he seems to do better. This year is much better in terms of him getting up and remembering all that needs to get done before he goes to school. Before school started we put a post it on the computer and he knows that if he does not remember he can go there and look - he maybe used it two days and has been pretty good since.

I have wanted to read Smart But Scattered for some time and it is on my list to buy as I think it might have really good tips for us. I am really organized, but somehow, I have trouble teaching him to be organized too - I just take care of it. So, like the OP, I am trying really hard to let him do it on his own.