Um, I do that. And I'm a little bit older than your son.
My mind gets distracted easily. It goes off on rabbit trails. Maybe it has something to do with having a creative brain, but I'm not sure. Not that I have to be on medication or anything, but when I'm doing one job and start thinking about another, I've lost my focus on what I'm doing and it's like I'm brain dead. (I think that's what happens when I put something away quickly and then completely forget where I put it. I wasn't thinking in the first place - I was just doing motions. I hope that's what it is. It *couldn't* be age!)
I've had to learn to focus directly on what I'm doing, take a short break if it's a long project, and then focus again for a while.
Games could be helpful. "I know there is ONE green sock on the floor of your room. Can you find it and bring it to me?" And when you send him to look for things, don't give him a long list of instructions to remember. Start small, with just one instruction. When he's good at following one direction, try two. Make it fun. Don't lose your cool.
Another thing that might help *you* understand your son is to go into his room, get down on the floor so you're his height, and look around. You may discover that it's a *really big room* with a lot of distraction-making stuff in it. It's good to see things from his perspective.
Just thoughts.
P.S. For your own benefit, when you're next at your local library, look in the children's section for Betty McDonald's MRS. PIGGLE-WIGGLE'S FARM. Read the chapter titled "The Can't Find It Cure." It'll make you smile.