I did a FiF for ..\..\..\build\output
FiF did nothing - no errors, no status, no search results.
Silence.
I had accidentally had Perl Reg ex enabled.
Feature request: When Regex is enabled, in the find dialog indicate invalid regular expressions in the find dialog - maybe with red squiggle underlines like spell checkers, or even change the outline color of the find or replace text boxes.
Also, disable the Find button while the expression is invalid.