Obliviousness

Does this seem par for the course for ADHD?  Yesterday, I put my husband's garbage (fast food wrappers, old receipts) that he had left in the car onto the passenger seat, so that he would be sure to see it when he got in the car when I picked him up from his job.  Well, mission not accomplished, because not only did he not seem to see the wrappers and receipts  but also he sat on them and then left them on the seat when he got out of the car at home.  

I kind of get "out of sight, out of mind," but "under butt, out of mind"?