My husband can be like this. He has ADHD and what we have learned after 30 years of marriage (we have known each other since we were 13) is that it is my HUSBAND needs to be the one to come up with the plan for remembering where he puts things.
This means some not so great looking locations, but they work for him.
My husband cannot use a typical drawer. If it placed away it is "gone" to him.
It has to be on top of something like a shelf at his eye level. Not in a box or a file.. But a flat table and right by the front door. Sometimes an open box type of a container like an open basket will work for catching things like his cell phone, Ipod, wallet, keys etc..
He is also good at keeping up with things on hooks. Hooks on the outside of the closet, by the front door (or whatever door he uses the most).
His closet is useless to him, but a clothing rack, is perfect. We keep one in our bedroom (it has wheels, so I can roll it out when we are expecting guests) and another rack in the garage next to the washer and dryer.
We keep his folded clothing that he uses every day in 2 chest of drawers, but only the top 2 drawers of the chest... They actually have a semi opaque fronts to them.. They are by Ikea..
He did best when he had stacking baskets in our old apt. when we first married, but they are not attractive. He could see everything..
So, watch your son closely and se where he naturally tends to "place" his things. See if he can come up with his own solutions. I know it is frustrating, but he is not alone.