Quite a few years ago. I had a similar issue with Getty Images. It was my own fault we were setting up a website for our business and used some images off google. At the time I had no idea about copyright etc
Anyway I got one of those emails and like yourself did a bit of research. Getty images clearly send out thousands of these emails to small businesses and blog owners.
In the end I ignored them with the proviso that if contacted again I would ask for proof of ownership of copyright. After two emails I never heard from them again.
Have never quite worked out whether it was a scam or if they send so many out that it isnít worth fighting or following up because so many people pay?