To leave a note/confront or not?

[Squint]

It also helps to have a smoker's sense of smell, so when the smell is 40% gone you will think it's 100% gone.

I would agree with this. At some point, you've cleaned out the majority of it, but a small portion remains that your noise/brain just tells you is the "normal" smell of the car. I haven't smelled the car you cleaned, ClutchDisc, so it's possible you did get it 99% clean...

But in my experience, most vehicles retain some portion of that smell - even if an effort is made to clean them.

[AHTOXA]

In my opinion, people who smoke in their cars just ruin the cars. The smell will never be gone completely.

...you can't even smell it if you bury your head in the seat and smell deep down in the cushion.

I don't even want to risk that in my own car. Who knows that kind of stale fart is trapped in there. That would ruin my day.