I don't know the dealer and have no dog in the fight, but I will say this, I work at a dealership and I have a demo. I generally don't keep a bunch of trash in my demo, but it's been known to happen. If I had a nickle for every time someone said they would be over to "buy" my demo, and no showed, I'd have enough for a couple cokes anyway.That's with just the demo I'm in now. Having said that, the car should have been taken and "freshened up" when you got there. As for the brand new issue, the car is still considered new in the eyes of the law until titled. No new car is titled until sold, up to that point they have certificates of origin. Regardless of mileage, your warranty clock starts at zero when you buy the car. The dealer should have noted that it was a "demonstrator" in the ad as well as told you as much when you called. That is just a bad practice on a salesman's part.
Not sure how many miles on a new car is acceptable to some people. We had a lady refuse a car that she ordered because it had 34 miles on it when it arrived at the shop. We tried to explain to her that it came to us 29 miles and we put the other 5 on during prep, and a trip to the gas station to top off. The 29 prior was factory. She wouldn't hear it, she didn't want anyone's butt behind the wheel but hers. I've seen cars come off the transporter with over 200 miles already on them.