Lost file on local server

Suddenly yesterday one of my key files disappeared on both my local and remote servers.  It's the file for my index (home) page.  The file is still somewhere, because if you go to the website, you see the home page.  So it's accessing the page from somewhere.  But I can't find it.  I did a search, and I've gone through every file and folder, and I can't find it.  Obviously, I need to find it so I can open it and keep updating it.  Help!!