Art thieves and the like

Well, to start with this sin't about someone using my art or plagerising as it would more or less be in my case....its more that i came across an image that I've seen for ever in a day  and someone else is claiming its theirs...Yes I'm aware that the obvious thing todo would be to report them but this image has been stolen a lot and from what I've read the orginal artist took the picture down and swapped accounts. so any ideas on what i should do? this is the image   and from my understanding it belongs to kankakanka.deviantart.com/ and you can see their water mark or intial which would be the K. I also don't understand why people can't make their own stuff and feel as though they need to take credit for someone else hard work. Rant done