Check section 20.1 (Searching and Replacing - page 211 in the version I have) to see if you’ve excluded some documents, either they’re not in the Draft, not Included in Compile, not in the Binder selection, etc.
If that doesn’t help (I suspect it will), check if you have “whole word” selected and the word appears with an apostrophe, it’s in a compound word, or another option is preventing find.
OK, stupid me… I had set search to “keywords only” a few days ago and forgot to set it back to to “all”. So, of course, it only searched the keywords. Duh!
This is an example of one of the little “gotcha’s” that every Scrivener user needs to be aware of.
Your reference to the Manual helped me spot the problem quickly. Thanks again.