[91LX2Bfast]

My Dad had to go lemon law on a '93 Pontiac Bonneville he had bought and I think the Pennsylvania law stated that the car had to have to same problem occur after they have tried 3 times to fix it. After that, you have a case for a new car. So if they fix it again, then it leaks, you should be able to go lemon law.
It sounds to me like someone bought it, then traded it right back in after they found the problem. Or the dealer used it as a demo because they knew of the problem. 500 miles is not a new car, but either way you SHOULD have checked the mileage. Go back and re-read all the papers you signed to see if it was listed as a new car, demo, or used. You can't prove anything they "said," so it'll all come down to what's on the paper/contract.