String locator can’t find string

Hi, i am trying to use string locator to find the PHP file/string and eventually manually edit coding of such file, but seems that when i am searching in the whole directory is not bringing back any results. I am not sure if I am missing something fairly easy here or I do have a bigger problem.
can u please help me understand?
result of search” Your search was completed, but no results were found.”

I always get this even if I am searching for a single word in a text which is clearly on my website.