I know it's a bit late to suggest this but for future reference you could have always followed the VBulletin model of sending DMCA/Legal threats to people who purchase the bootlegged software.
I realize this doesn't make you any friends but if enough of those customers disputed the charges with the person who had stolen your software you may have been able to put him out of business.
I actually contacted most of them because the software was sold in a small community. I offered them immunity from legal threats in exchange for registering with me so that I knew how many people had purchased. The plan is to sell them official upgrades as their current unsupported versions become outdated.
I realize this doesn't make you any friends but if enough of those customers disputed the charges with the person who had stolen your software you may have been able to put him out of business.