I've never tried a public library.
Last summer I typed Jehovah's Witness into my university library computer to find about five anti-jw's, two where they were just mentioned in a few paragraphs about millenium churches or cults, and about four from the Watchtower and tract society. They were all shelved together in the religion section of books.
All of the ones in my search list showed up on the shelf. So it is possible the dubs in my area are slacking and forgot about the Univ. library.
Honestly it wouldn't surprise me at all that this was going on at library's all over the place. Do you think they count their time when they go out searching for and removing apostate lit? I would have...hahaha!