Getting a Warning on Build: "Script attached to 'prefab_Name' in scene '' is missing or no valid script is attached." However the prefab it is referring to, as well as the script, have been deleted.

My guess is that there some sort of meta file somewhere that is tricking is into thinking this prefab still exists. If so how would I go about locating and editing that file?

Thanks in advance for any help.

I had the same problem after upgrading to Unity 2019.2.10f1.

To fix I went to Window menu > Package Manager

Then update the Multiplayer HLAPI package. I updated from 1.0.2 to 1.0.4, after that the errors went away

Check your scene for a prefab that you deleted from the project folder.
It is usually colored red in hierarchy.

try this :
from asset folder >> right click >> Re Import All