Finder and Spotlight do not return the expected results when searching

Am I right that Spotlight or the Finder should search the contents of a file?

When I search the Finder or Spotlight for a word in a text document (.txt) or RTF, it returns nothing.
Example: I have a simple RTF or TXT file in Documents that contains the word "car".

Neither one nor the other returns nothing:
contains: car
like: rtf contains: car
genre: txt contains: car
kind: the text contains: car

the document has been around for weeks, so it should have been indexed.

All projector settings are the default settings (all that is selected).
I use Mojave in a Mac Mini 2014.

Any help is welcome.