robots.txt file has been altered but not seeing the alteration in the liquid file

I got a note today that my robots.txt file was altered. When I look at the front end (ie., .com/robots.txt) it is indeed altered. But when I look at what it actually in my liquid file, it’s how it was when originally launched. How is this possible and who could have altered the file? Many pages have been disallowed that I want search engines to find. I can’t figure out where this file is so I can’t fix it.