If you registred your BUID with your account back then, check out Account - Product Updates. You don't need the BUID anymore after adding it to your account.
If you didn't register it, you will need your payment recipe to proof your buy I fear. (assuming you bought it through www.blitzbasic.com, not from someone else selling it. In that case you are most likely out of luck)
If you didn't register it, you will need your payment recipe to proof your buy I fear. (assuming you bought it through www.blitzbasic.com, not from someone else selling it. In that case you are most likely out of luck)