I tend to not stress over stuff like this, I don't like to waste the mental capacity on petty theft like this. I often get messages and things about people stealing my work. I only get annoyed If they are making money off of it
.. There was a case a while ago where a facebook game named mech commander or something,.. they had stolen a render of the fiddler Mech I made and used it as an advert to attract players.. not cool
.. occasionally I will do a reverse image search on google. This shows me allot of places that take my work and do things with it, 95% of the time they are just on wallpaper websites ect.. and most of the time they give me the credit and a link back to my deviant art page which is nice