There is no glitch. And, you've already answered your question!
You made a backup on the CD. Good. Take out the CD and store it safely somewhere. Open and work on the book project from your hard drive. And, yes, ID always wants to write upon Close of the file, even if you've "done nothing", sts. (A mere view change or different page from the opening page constitutes a change - even tho' you've "done nothing"!) ~S.