Yep, one day at a time. Might seem like chaos some days, but it works out in the end. Thinking of you!

I know this isn't about just forgetting the key, but I bet he remembers his key the next time, and if he doesn't he will eventually. lol

Use some of those sticky notes or those coloured dots. At one time I had those everywhere. Diff. colours for diff. things. After a while they become subliminal. Put a bright red one on the door where he leaves the house then it'll remind him everytime to check that he's got his key before he leaves. Got to have a conversation with him about it first of course so he knows what that red dot is all about. lol