The spammer scammers are uploading volumes of plagiarized work off of websites like Wordpress, putting them in zip files and selling them to people like the one that stole Agentkirb's book, who then self publish dozens of books at a time. There is no systematic way for Agentkirb to find the stolen work for sale, and in fact, it could very well be that other people have also published the same story under different names. In addition, whoever Jessica really is may have already relisted his book with different titles and a different pen name. You are only considering the tip of the iceberg. There's an overwhelming problem here beyond removing a couple stolen books. It threatens to make the whole self publishing system collapse. I think at the moment it may even be possible for someone to retype any less than famous book, change a few words, then list it as their own. It may sound far fetched, but it isn't. It would mean anything you try to e-publish had only meaningless copyright protection, and anything you buy on Kindle may be stolen property.
With the internet, plagiarism has become a massive problem. Nobody's denying that or ignoring that. But that's a different issue from blaming the bookseller for not catching it. Protecting one's copyright has always been the job of the writer and their publisher - NOT the bookseller. Is that a problem for self-publishers? Of course it is. That doesn't mean the burden should shift to the bookseller. It just means here's another issue the author (and as their own publisher) needs to deal with. Another of those unfortunate side-effects of self-publishing that people don't want to acknowledge.
I didn't know there was a question. I agreed that plagiarism is a big problem - I have no interest in moving to another thread for further discussion of your opinion that booksellers should police this.