my zen cart site went missing

my zen cart store seems to have gone missing. The admin backend/pages seem to work fine, and the server is serving images and our web email fine. Just the actual store front is a blank page, with no error shown.

As far as I know we have not made any changes or uploads to the server recently. Looking at the server in filezilla I don't see anything of note with recent modified dates apparently out store has been like this for 24-36 hours. Any idea what happened or how to fix this?

https://www.thinkbamboo.com

there are lots of files and folders since we put zen cart at the top level of our domain after hosting a older site there.

tried replacing the files in this thread

http://www.zen-cart.com/forum/showthread.php?t=108879

site still isn't working.

I have had a chance to talk to everyone who works on the site and no one has made any changes or updates recently. Site had been running smoothly without any changes since October or so. We got our last order on the 9th. As I said before the admin backend works fine its just all the catalog pages are blank.

I have tried replacing the .htaccess and the index.php file at the root of the site but that hasn't worked.

We run multiple domains on a shared server, one of our other domains on the same server runs a test version of zen cart. This test store is loading properly so I do not believe it is a a problem with our host.