Funnily enough I deal with a similar topic to this situation quite regularly with the action sports photography, my opinion on this is if it’s used for social purposes where no money is made I’m all good with people using it, for example, showing a friend the photo or using it on Facebook, free publicity as it has my metadata and watermark on them. If however I find out that it’s used commercial then that’s a completely different issue which I can drag in copyright and fair use laws to sort out the situation. Generally if it’s a paid job I’ll protect the photos under Creative Commons licensing and so will reach out to them in the event of a photo being wrongly used, also to send an email to the person using the photo.
I appreciate when someone asks whether they can use the photo and tells me how they’re going to, generally I will say yes. If a person uses the photo to edit and remix them again I’m fairly free flowing about that, I’m more intrigued to find out what that persons vision is of that photo, how would they have taken it instead. If a photograph was deliberately stolen and used the create money, such as a stock image site, then the creator should be in contact with the person first. If that person is hostile or refuses then the creator could proceed with getting the photo removed and properly copyright or watermarked, also pursuing the accused person if serious.
Acknowledgement for the original creator though is a must no matter how manipulated the photo has been, similarly to music remixes. Bringing the used photo into my own practice through emailing the person responsible for the editing, I’d ask if I could promote the image (depending if its well done) on my website and social media sites. Physically though maybe not but it would depend on the circumstances.