I had a similar issue once with someone in America. With the help of others we tracked down their address, local police station and I continued to post/bump threads on all forums they sold on to flag their behaviour to others. I also continued to message them and the threat of reporting them to their local police establishment seemed to finally do the trick and I did get my money back.
Karma is great, but not everyone can afford to throw good money away on a lesson learned by being scammed/robbed/duped or whatever you want to call it.
I'd say persevere with trying to get their attention and also warn others via threads and replies to any of their sale posts on other forums. If nothing comes of it, you will at least have the satisfaction you've done what you can to warn others who could end up with the same fate as you.