In any version of Revit 2012, a user can rearrange the panels in the Ribbon interface to suit their work flow.
There is a way to reset the Ribbon interface so that the panels return to their original position.
Locate and delete the UIState.dat file. For Revit MEP 2012, in my computer the file is in the following location (Windows 7):
C:\Users\mrotolo\AppData\Roaming\Autodesk\Revit\Autodesk Revit MEP 2012
WARNING: Deleting this file will also remove any customization done in the Quick Access Toolbar. I would recommend making a backup of this file before deleting.