1. if you bought it instantly after your first one it must be, 5014, or 5013. because 20,000 ID's of blockland, isn't a lot. (roblox: 3,000,000 members, so, a account must be made on roblox, every 10 minutes.)
One key maybe made, every, 25 minutes, on blockland.
2. try re-sending the key, to the e-mail it used? or maybe check the e-mail system, and see if theres a glitch you can fix, that collects e-mails correctly. (MAYBE, I'M JUST BRAIN STORMING)
http://blockland.us/index.asp?p=SupportLost key recovery. try re-sending it.