I used a photo from a Google search on Facebook that had no copyright symbol, watermarks or artist credit, although I looked. Now, a year later, some company (seemingly legit.) says I owe the photographer $500. This photo appears in many places on the web, but nowhere that I could see was the photographer given credit and there was no indication of a copyright. Once this law firm (?) gave me the photographer's name I located a UK newspaper source showing he won a photo contest and I assume that is the source of the original photo that is now spread all over the web. Telling me I owe $500 is like saying I missed the invisible price tag on the item I found on the street. Do I have any legal standing here?