According to that link, Confucius and Muhammad also appear on the U.S. Supreme Court building, along with Moses. Is sounds like the Ten Commandments are only depicted as the numerals I to X.
Moses, in the center of the frieze on the East
http://www.supremecourt.gov/about/East_Pediment_11132013.pdf
Govt persons on the West
http://www.supremecourt.gov/about/westpediment.pdf
No mohammad.