When I search in the spotlight for a locked note, I can see the content of that looked note. I went ahead and rebuilt the spotlight index, but still showing the content. Am I missing something here or is it a bug? OSX-ELCapitan 10.11.5
You need to close your notes
I justed tested this in OS 10.11.5 and the contents of the note don't show, just the title.
I created a note and titled it for which it would be easy for Spotlight to find: "Smattering test note" (I have no other instance of "Smattering" on my system). Here is what it looks like after I have locked and closed the note.
Doing a Spotlight search for "Smattering" yields this result:
It autocompletes the note title (ligher grey text) and clicking on it opens the Notes App. Until I unlock the note with my password, the contents are not visible.
If I don't lock and close my notes, if I do a Spotlight search, the contents will be visible