I would have done the same as you and just took my chances as a walk-in. Did they inform you of a charge for a no-show? If not and they are just taking cc #s to make you somehow feel more committed, then if I wanted a rez that badly I would probably scramble a few digits. In general I don't even like the custom in this country of a server disappearing with your card as opposed to the tableside method in Europe, and I certainly don't like the idea of my cc# floating around on a piece of paper in a restaurant.