You are correct that you have found the file /etc/X11/xorg.conf empty !
And how does the xserver find the correct configuration file?
The reason for this is that Xorg now made a big decision to move the project forward on its input system.
Xorg.7.4: at the same time this will allow the great majority of users to run without a /etc/X11/xorg.conf file. (For example, Ubuntu 9.04 uses this feature)
Now Xorg will depend on dbus(desktop bus) and hal(hardware abstraction layer) to handle hot-plugging. Why? "Xorg did not need dbus and hal before," many people ask. The reason is decoupling. If Xorg has to handle all these by itself, the codebase becomes complex and it duplicates functionality. Decoupling is good. This way we have less bugs, better design, and faster development time.
To read more, here