if you haven't yet, register here Home Page - Buddy Auth Portal using the same e-mail you used during checkout. once you get in you should be able to view your keys.
if your sure that the e-mail you created the buddy auth account with is correct, and its not showing up. double check your e-mail and make sure your key didnt get lost in your spam folders. if you still cant find it, send an e-mail to support@thebuddyforum.com so they can retrieve your key manually.