What a bugger Harry !!
May I ask what was the artwork was doing on the net open to public view ? if was only for use in a private book being written..
Artwork is especially hard to copyright and copying it is all too common online..
Has your friend got or hold a full copyright on this actual piece of work yet?

I have this picture in my head of a Russian trying to figure out WTF would be wrong with right clicking and saving a few pics...

Hope you find someone to help your friend and have some luck mate ...