My gconf_editor has no button_layout key or any other key only the theme name key is there.
Kindly elaborate your question. Mentioning your type of Ubuntu, version of Gnome if not unity if you are using it to get button layout and where you are trying to search button_layout>
or else if not possible atleast a snap shot
For GNOME SHELL.
Basically it should have been, desktop>gnome>shell And you have to change the "Arrangement of buttons in titlebar" in shell