Did you mail it USPS? Is it going out of state? If you answered yes to these questions GET A LAWYER to look into it. As Chimera said have a friend go see if there are cameras inside, in the parking lot, traffic cams, they can have you mailing it, getting into your car, your plate number. They have all kinds of cop stuff these days, you should not just hope for the best. Interstate mailing is one of the things they take seriously. I am not trying to make you paranoid, but they have already called you, a knock on you door could be next...