This is the fiirst time I have ever heard of something like that happening !!
I didn't even know something like this was possble. You made the deal, signed over your original car, signed THEIR contracts, then they have the "right" to basically say. "oh, nevermind" and you have to bring back the car ??
I was under the impression that once everything was signed, it was yours. You had to disclose what you earned, what your bills were, etc., when you filled out the paperwork. They knew before you left (unless you weren't honest in your figures and fudged some numbers).
Be that as it may, you drove that car for two days, it is no longer considered New and can not be sold that way. See if you can strike a deal on your "now-used" car and keep it !!