HELLPP my index.php is gone!

my website is https://www.e-bookreaders.biz

I receive alot of visitors everyday, but since my site is down im going to lose them, i don’t know what happen, but i contacted my webhost, and they said my index.php was missing, and now my site shows an index of my directory. I tried to download wordpress 2.5.1 index.php , and uploaded into my web directory, but it gave this error message:

Warning: require(./wp-blog-header.php) [function.require]: failed to open stream: No such file or directory in /home1/ebookrea/public_html/index.php on line 4

Fatal error: require() [function.require]: Failed opening required ‘./wp-blog-header.php’ (include_path=’.:/usr/lib/php’) in /home1/ebookrea/public_html/index.php on line 4

Plezse help, i need to get my site back up and running, i started receiving alot of visitors,.. thank you!

my website is https://www.e-bookreaders.biz