Not to let the publisher off the hook, but there’s a good chance your photos were uploaded to some sort of content management system along with other photos that they actually licensed, and someone in the organization found yours and assumed they were licensed.
If you hope to work with this publisher again, $200 is on the very low side but won’t burn a bridge. If you don’t expect to work with them again, I’d invoice more like $1000 – search for some legalese to include in your communications with them.
I’m assuming your info was in the metadata and that’s how they knew to credit you? It’s a good lesson for artists to populate those metadata fields before sharing work with clients.
Because I’ve seen it happen first-hand. The metadata fields get automatically pulled over into the content management system, but there’s no field for “this has been properly licensed and here are the terms,” at least in the one I’ve seen. It’s a flaw, to be sure. Irresponsible but not nefarious.