It's easy to view a list of all of your past purchases on WarriorPlus.
The "Purchase History" system was created just for this purpose. It is available to anyone with a WarriorPlus account (FREE).
The purchase history page can be found by clicking on your username in the upper right hand corner. Then click on "My Account" and then on "Purchase History".
Or, you can access it directly here: https://www.warriorplus.com/buy/history
Simply follow the instructions on the page to verify your email address(es) you use to make purchases, and your past purchases will appear.