I've contacted them about this, as this has been a new development for me. I had been a happy subscriber for nearly a year (until the last 2 updates, when the app started lagging and freezing constantly).
I am also annoyed with doing a search and having books that aren't available showing up with the 'not available' banner across it. It's annoying and kind of feels like a slap in the face. I would rather have the title not show up at all than the air of having someone thumb their nose at me by telling me that some people can view the book but I can't.
(I do realize it's not personal and no one is trying to thumb their noses, but I feel annoyed when I see those search results, especially when I have only come across this in the past week. Whatever change Scribd made, it's disappointing. They may soon lose me as a customer. The only reason I was tolerating the buggy app was that I liked their book selection.)