Eventually, after failing to find a roommate, Sheldon resorted to turning his life back to the way it was before he met Leonard in 2003, even going so far as to changing the apartment's layout to its 2003 setting, with everything from before then inside Leonard's room. He really wanted to have Chris Pratt as a roommate if he was willing to take the smaller bedroom {Leonard's old bedroom}. His people never returned Sheldon's messages. Final solution was to have the Hofstadters spend at least half the week sleeping in Apartment 4A, to accommodate for Sheldon not being lonely.