If you sent the MSPA $15 and took their "Silver Certification" test then they should have sent you a certification number. If you want more information about their program, their website is [
www.mysteryshop.org] Read through their FAQ because they indicate that there is no guarantee that being certified will get you more jobs etc. They carefully state, "Certification may give you an edge with some companies. Imagine two shoppers in the same town, with the same experience and work performance. One is certified and one is not. All other things being equal, the certification sets one shopper above the other with some companies."
Certainly certification is not required to shop. There are a small number of companies that do seem to give preference to certified shoppers and they seem to be companies most deeply involved with the MSPA. There are a huge number of other companies out there who don't give a hoot if you are certified or not. They are much more interested in how you have performed on jobs for THEM and what kind of education and experience you have. So it is free choice whether you decide to spend $15 to buy a certification or just get on with mystery shopping. It is possible to do quite well in this business without it.