How can I find the file some element is loaded from?

I manage a website which is based on Drupal CMS. I have FTP access and I want to modify the structure of the header.

I know that the header is loaded from separated php file but I don’t know what is the path to the file and how to find it in FTP.

Is there any way in Chrome dev tools to find the path to the file and is there a general way to find the files from which some part is loaded?

Why doesn’t Chrome see my CSS files in it’s Coverage tab on my local development environment?

I’ve got a vagrant environment where I do some Drupal 7 development and I wanted to remove some unused CSS. So, I hit the record button and started loading pages. JavaScript files were picked up fine. And so were some external CSS files. But, it would not find any CSS.

I thought perhaps it was because of Drupal 7’s practice of adding a query string to the end of its CSS and JS files, so I stopped Drupal from doing that. But still, it’s not finding the CSS files. Any ideas why it wouldn’t?