Sorry to hear that SkinMan...your stuff is great.
Adding anything to the mesh or textures would only work for awhile...after someone was presented with the evidence of misdeeds, the info would be out very quickly. The only true way to fight it is with self-policing. If you see something credited to someone, and you know it was done by someone else, speak up. Sometimes it's a mistake, the readme was lost and the model was credited to whoever posted it; sometimes it's purposeful, and those are the ones we need to know about. Then we can find out all the places they go, and present our cases to their friends/acquaitences(sp?)...discredit them enough and they might go away.
And yes, even if you're not a modeler/texturer, just a fan, speak up...you have more say than us actually because you ARE a fan...you know the work, but had nothing to do with the work.
Unfortunately, this is often the result...a great asset to the community lost because someone couldn't be honest. And I thought most of us were adults...