robots.txt file exists but I can’t find it

I have a site which I set to public in the privacy settings but somehow google webmaster keeps detecting a robots.txt file in the root folder that is disallowing robot crawls for all pages.

When I look on my server I do not see the existence of a robots.txt file. I even tried and create one that says “allow” and it did not change anything. I also upgraded to the latest version of wordpress.

Where can this robots.txt file be coming from and how do I get rid of it and start getting traffic?