https://www.usps.com/manage/informed-delivery.htm
The initial problem was that her mail got stolen by the mail person. USPS Informed Delivery would have told showed her the letter that she should have gotten since it came to the processing center nearest her local post office.
Informed Delivery also shows you tax mail (like W2s) that get mailed and are commonly stolen with informed delivery you know when they are mailed to you.
>But there was one last twist to the mystery. Sue Brennan, a spokesperson for the Postal Service, explained that my credit card was scanned at the processing center nearest to my local post office. Which means that the thieves stole it in New York City on July 16 and took it all the way back to Ohio in time for its big day of spending at the mall on July 22.
>Two months after my hack, on September 29, federal prosecutors in New York announced that they had busted up a scheme that sounded familiar. Three postal workers were charged with stealing credit cards out of the mail and passing them on to five "shoppers," who used them to buy luxury clothes and bags at stores like Chanel and Hermès that they could resell online.