If a book exists in PDF on the web somewhere, I estimate a 90% of chance of finding it by at least one of the following four methods, which altogether take only a few minutes if you’re practiced at it:
Search library.nu. (You’ll have to sign up for a free account the first time.)
Search Library Genesis.
Search Scrapetorrent.
Use a custom Google search and keeping clicking through links until you find a filesharing site link for the book—one that isn’t broken yet.
“All that your brain does when you ask it a question is hit “search” and return the first hit it finds” is saying roughly the same thing that Stanovich and other researchers have said about ‘default to Type 1 processing’, as explained recently in this post.