I am having a big problem finding the settings.js file in my NR install. I am running it on Rasbian Stretch, and I have tried to update it with the script in the documentation:
then the startup messages will show you where settings.js is. Since you installed using the pi script then, as @ukmoose said, it should be in the .node-red folder in the home folder of the user that you were logged in as when you ran the script.
So, there was no settings file for the first few times that I ran the stop and start, as @Colin suggested, but I rebooted the Pi a few times and redid the stop/start a number of times, and it eventually appeared. Not sure why that was the case, but thank you for your help!
When you ran it those first few times what did the start log say about the settingsfile?
If it said that it was in .node-red as expected then perhaps it was a caching issue with whatever you were using to determine whether the file was there or not.
I don't recall seeing any indication of a settings file at all, but that program ran smoothly. This was the main source of confusion; the whole NodeRed install seemed to be running without any settings at all.
I used exactly the same commands to open the directory now to see if the file was in there - I can't really think how I could have done it differently this time. Perhaps I started with: