Crooks get credit card information in many different ways. Going through the trash is one very low tech way. Meth addicts have been known to use their extra hours awake to reassemble shredded documents for ID theft, including all the mail with the credit card offers. A high tech way to get credit card info is to use skimmers, small devices that record account information. Make sure that card readers at gas stations or other locations work normally and if there is a problem, look for any unusual devices on the reader itself. Crooks sometimes put their own skimmers on and can be very hard to detect.