Need help searching in sub-folders?

I know in the top right corner I can do a search. But sometimes it will look in all sub folders, and sometimes clearly not since it gives me zero results.

This search field only uses the files you have selected or pointed to in the content panel. For proper searching with lot's of options and ability to chose the source, including subfolders and non indexed files you need to use the dedicated Find command Edit / Find or cmd +F on a Mac