They are discovered by book lovers who lovingly bring them home and read them. In time,they will release them. They might or might not enter this info into the web site.
They are discovered by the owners of the stores or managers of the locations near where I left them and thrown into the trash.
They are discovered by people who don't give a damn about books and either left where they were or dropped somewhere else and forgotten.
Of course I want to think that they are not thrown away. That's the worst thing that could happen to them. But I have no control over them and that alone is freeing and maybe even cleansing, in a way. Not that I believe in "cleansing". heh.