Art Theft and Illegal Use..... for profit

So tell me.... What would you do if you came across someone's artwork being used on on eBay as their product or part of their product? I have found stickers, automotive decals, t-shirts, custom printed car tags, steering wheels speed knobs, buttons.... and much more. I have located several of the artist here on DA and notified them of my finds. I have only received one reply out of the seven artist that I have notified. I have checked eBay and the items are still listed. Should I continue to notify artist of my findings or just leave it alone? I thought I was helping out. But maybe I am just sticking my nose where it shouldn't be?