Using ID 17.0.01 x64 on Windows 11, when closing all files, but not the .indb file, the files disappear and and screen reverts to the opening screen. Under Window, the book file appears and when clicking on it, the book file shows up in the upper left hand corner of the screen. Not where I put it at the top of the right panel. Plus, it shows the last file closed wasn't saved in the book.
Previously, the book file remained open, visible where I placed it, and the files were saved and showing saved.