That's too bad. I have bought many bikes without riding first, because they were not in riding shape. I have also skipped bikes that rode fine, because they had visible crash damage. Is there any obvious sign of collision? Ripples, dings, paint stress marks? If not, it may be a simple fix to re-align the frame. How about some pictures?

EDIT: I have also had bikes show wobbles once past 40mph, obviously hard to do on a test ride.