Pictures from your first post:
1st picture shows your library is called "Calibre Library"
2nd picture looks like you did a search for the ebook. The path does not contain "Calibre Library"
3rd picture is the Calibre? viewer. I assume that you opened the ebook from your search and you have your system set to use the Calibre viewer. I believe you can use it outside of Calibre.
I may be wrong (I am just a novice Calibre user myself) but it appears you may have moved your ebook out of the Calibre Library. If it was me, I would just go to Edit Metadata and in the upper right hand corner select "Add a format to this book" (red rectangle with +). Find your ebook and add it.
I am using Windows XP so your system may not show the same path info mine does.