When it comes to history reports the two main players are AutoCheck VS Carfax, and my vote goes to AutoCheck, if you care to know why you will find a full explanation on my website, I cannot give you a proper answer as to the response you got from AuotCheck as I don't know the full details, but I trust their decision.

As for you having any rights navigate to this link http://www.usedcartips.org/dispute.html

Now lets be honest and face some facts, buying any vehicle is a process of steps that many consumers don't follow, in your case, step one, why did you not take vehicle for an independent inspection prior to purchase ?

It tick me off the salesman got away with telling you, a fender bender, nothing major, knowing quite well about the frame damage, you will have rights if you can prove misrepresentation, but only legal counsel will know,enter your complaint in the link I provided.