Google tracks the
chillingeffects.org complaints and I think the other SE's do as well. This will also get the thiefs host worried as ultimately the host is responsible for everything on their server whether they put it there or not. Threatening to include them in a lawsuit with the backing of Chillingeffects.org should get most hosts to sit up and listen. Lastly to proove your content is the true copyright holder check the
wayback machine. If you aren't blocking it they will have all your content likely indexed and dated. If you're incredibly lucky you can also find out when the other site added your content.