I've seen that happen with Dreamwidth and even very old Livejournal posts, too, without any notification of the authors that stuff they wrote maybe 15 years ago is now going to be in a searchable wiki. (Dreamwidth and LJ both let people opt out of being searchable IIRC and AO3 gives you the option of not letting Google et al index your work. Which is often a lost cause but at least it's an option.)