Whatever treatment he’s getting, if any, it’s not effing enough.

wow... that day definitely sucked.i feel for you. that being said..... why the hell is he not on meds, and why did you not prepare better aka keep a closer eye on him for that one special day? that's kinda on you. so yourself a favor and get him some meds.

I have ADD. You should have screamed in his face. It can be managed by developing habits like ALWAYS, and I mean always, checking your pockets before you leave the house and ALWAYS being aware of where keys are or putting them in a specific place. The thing is, it takes an incentive to develop these habits, like missing a flight or getting fired from a job or having your mother scream at you or sorely disappointing your family. Also, if you don't let him know how angry you are, you will just become more and more resentful until one day you just lose your shit and possibly assault him. You can punish him or life can. Life does it much harder.

I suggest that son is simply not responsible enough to have free access to your car keys. Keep them under your control if you have only one car. Make sure he only gets them by specifically asking for them so you can make sure your transportation needs are always assured… I agree that everyone, including ADHD individuals, need to deal with the consequences of their choices and failures. It’s not smart to shield them from the consequences of what they do or fail to do if you expect them to ever be functioning individuals in our society. While they might shielded from those consequences early on by their parents, ultimately life will not shield them and it’s better to face reasonable consequences now than abject failure later… By the way I have a son who was diagnosed with ADHD when he was young. It was a very difficult time when he was in school. I think my wife (now my ex) may have made it actually worse by doing most of his homework for him so many times so that he simply never functioned well in school. He eventually earned a GED. But most people with ADHD can learn skills. My son responded well to the structure of martial arts courses for children and young adults and it was something he felt good about - a new skill, a new belt color. Eventually he worked mainly in security or sometimes in construction. Those fields fit him better than school or office work. People have different interests and abilities - The point is we all have to learn life skills and work skills or be forever dependent.