The thing is the car does probably exist somewhere - but it may be in their system, but allocated to someone (on paper only, because if they allocate it in the system it disappears from the website, but they want you to come in), or in transit (they appear on the website the moment the factory assigns a VIN build to the dealer, etc.
And sometimes I swear it's just a glitch and they don't really care.
In my case it wasn't that: The dealer straight up imagined a sale they wanted to have, and were quite rude to me.
Me: "I want to buy one of the cars you advertised in the newspaper." (It was 2003)
Them: "We don't have those cars."
Me: "But you're advertising this sale."
Them: Poker face.
It wasn't like they said, "Oh, yeah, that was a popular sale and they sold out." It was very clear they advertised cars they didn't have so they could divert me to a more expensive model, and it wasn't like they offered to call another dealer to ask if they still had inventory.
>And I get that some of the walking around is probably a ruse
I don't doubt that on a slow day a salesperson and the entire process will be slowed down... nothing like tapping into the sunk cost fallacy (as a buyer I spent 3 hours here today, I'm not walking out now and doing THIS again)!
It's merely a gimmick to get you in the door and convince you to buy something else. (And probably illegal, too.)
Happened to me the first time I went to buy a car. I just walked out and went to a different dealer.