We had this same issue. With Details too. This is a simple solution that @Amanda Marin shared with me years ago (Thanks Amanda) that works for both Details and Ref Notes.
Create a detail. Save it as Non-applicable in a new folder in your LandFX details folder. All that's in the detail is a template titled NON-APPLICABLE.
Open and save a drawing as NON-APPLICABLE.
Add that drawing to the Project Manager. Call the sheet "A"
Insert the NON-APPLICABLE detail to the sheet A. When asked to place it as number 1. reject and call it "N".
At this point, you have a detail called "N" on a sheet called "A".
Now when you have any Details or Ref Notes that don't have details to show, you can assign the detail "N" on Sheet A".
When you run a schedule all of those elements will have their columns automatically populated with N/A.
Ta da!