Two important things for you today:
TipOne: Delete any views that are temporary or unused.
I wish this went without saying, but.. When you're in the process of working on a specific project, you are going to have to create various project views. In many situations, you are most likely going to require hundreds of various views for a building that is complicated and large (typical). You should always look through your views and try to find any that you have originally created for visual and temporary reasons (that you are not using any longer).. and delete them. Not only is this going to result in your project being leaner, meaner and cleaner.. but it will also increase file performance speeds.
TipTwo: Quickly View all views NOT on Sheets.
You already know that if an Elevation, Section or Callout view is NOT on a sheet, it will NOT have a detail/sheet number reference. But if you want to quickly SEE which views are not on sheets (in the Project Browser).. Switch the 'filter' of your Project Browser.
Here's How: Select View>User Interface>Browser Organization
Switch the Browser Organization for Views to 'not on Sheets'. Once this is done.. your Browser will ONLY show views that are NOT on Sheets. You can then see if you have accidentally not placed a detail (or other view) that was supposed to be part of the Drawing Set. And you can easily open views to see if they are needed any longer.. good candidates for deletion/ retirement.
*NOTE: Don't' forget to switch your Browser Organization back to normal! Whatever 'normal' is for you.