No problem, this kind of thing happens.
That being said, I did uses the same e-mail address here than on Paypal. I can send you my Paypal receipt by private message as proof if you want. It's worth noting though that I registered on the forum only after buying the license, but that doesn't matter, does it? If it does, you shouldn't be able to buy the license without being a forum member, it's quite confusing otherwise.