There's a few revelations from this about RPG community norms:
1) The assumption that nobody would do this "normally" -- i.e., no random GM would replace every proper noun for their game world for their own purposes (I have done exactly this) for private use. It's possible (but increasingly unlikely) that it was done by someone who was just submitting their own homebrew version.
2) That there is some magical tool to check plagiarism on the Internet (in academia of course there is), and that companies actually use them (in reality, very few probably do). The odds of a video game publisher doing so is even lower.
Mike