I am not sure whether this is a bug or a feature but I have noticed that Sublime Text can “steal” search criteria from Mail application (macOS).
This might be confusing in case one searches in files for something and jumps to Mail to look for something else. In that case, Mail search criteria overwrite “Find in Files” that was specified inside Sublime Text.
Is it intended behaviour?
macOS has a find clipboard that’s shared between all applications. This is standard behavior that you’ll find everywhere. You can disable it using the "use_find_clipboard" setting.
I guess the thinking behind the OS feature is to give the ability to quickly search for the same thing in multiple applications without having to Cmd-C the search term (and hence clobber something important which might be on the normal clipboard).
Thanks! Now it’s clear. Always learning 
I will follow your advice with use_find_clipboard
