When I made my purchase, I got an email titled "Order confirmation" along with an ID number.    In the email, you have a link that will take you to Renderosity to see your order.  In the summary, there's the title of the product you bought e.g. "Poser 11 for Windows and MAC" and right underneath it for me, was the license number that I then used to log in and get my download of Poser 11.

I hope that helps.