When doing a search and replace using Regular Expressions, an error message will come up at the end saying "Find Result: The search text "your search text" was not found."
"Your search text" will be replaced with whatever value you searched for.
This message is in spite of the fact that the value was found, possibly hundreds of times or possibly just once, and accurately replaced.
Further, search and replace by Regular Expressions only works if the text being searched is highlighted.
Searching a file from the top with Direction set to "Forward" will always generate no matches, even if matches exist.