I was contacted by Copytrack and I am in the same situation. I used a photograph of a band I found on their facebook page on an article and credited the author, both in the article and in the link of the photograph. Apparently, this wasn't not enough, and I was hit with the email to buy the photo. I contacted the photographer directly, she said she can't get involved in this issue anymore, as it is out of her hands.
I run a blog that generates no income, and it's not a legally constituted company. It isn't even registered anywhere.... it is just a digital blog. I am currently unemployed and have no assets under my name they can come after, so I have no means of paying the €400 they ask. The blog is hosted in Portugal. I replied saying I sourced the photograph, they didn't care. So I emailed back stating my current situation and I'm still waiting for a reply.
Is a lawsuit likely to happen in this scenario? How did other situations evolve?