That sucks. I have it happen alot. I tend to find alot of stolen galleries via google and sponsor stats. I always contact the tgp's that the recips belong to found on the stolen galleries. 50 percent of the time they have blacklisted my "sponsor codes", But quickly explaining the situation gets blacklist removed. 9 times out of ten they don't understand why they leave my sponsor codes.
I ronically there is one stolen gallery that keeps netting me sales. Gets lots of google traffic. It's recipless too.
