Providing you bought Pro from the official site Lime Wire » Official Website & Free Download, BitTorrent « go to this page...
Lime Wire » LimeWire PRO Lookup
...& enter every email address that could possible have been used to buy Pro!

If that doesn't work & you were the one who used your credit card to buy Pro, send a PM to limenathan & see if he can help you sort it out.
limenathan