Use the copy from your backup, or the original download if you are convinced that really might be the issue. Otherwise, you should probably be able to log into the members portal and re-download it here.
http://my.studiopress.com/themes/quattro/
I do not have access to anything other than the wordpress dashboard. No access to the domain account or server account. I was only granted access to the wordpress account as an administrator.
Unfortunately, that information doesn’t change where you can get a copy of the original functions.php file from. You need to either get it from the person who bought it, obtain a copy from their backup files, or get their studiopress account information and re-download it.
