If the shipping service provided a tracking number, use it on their website to see when the money order was delivered. If you want to know if a money order has been cashed, the method depends on the issuer. Some let you put the money order's serial number on their website, while others let you enter details on an automated phone call. If you do not have a receipt, go back to the original issuer with the details of your purchase to see what your options are.