Our site (my employer’s site) is on a simple HostGator business account.
The only plug-in we have in common is Google Analytics Dashboard.
Yeah, writing code to auto-upload the .php files beyond the scope of my skill set, but I am wasting an enormous amount of time with this as well. Hopefully we will get a response from someone useful soon.
I am having exactly the same problem (post.php file disappears from wp-includes and wp-admin/includes every couple of days, breaking the site). I too, am able to temporarily fix it by overwriting the wp-includes and wp-admin folders, but it continues to happen.
