even without considering that you charge an anonymous card with your bank account, if you keep only one, it's quite easy to follow patterns still. Especially if

even without considering that you charge an anonymous card with your bank account, if you keep only one, it's quite easy to follow patterns still. Especially if they have already targeted a person and they have additional information, there are not so many people that check in X and check out Y on days W,Z.. and so on. The more additional info you have, the narrower the search space.