That couldn't be possible. Planes take off all the time with just two pilots on board. If one goes to the lavoratory, that means there is just one pilot in the cockpit at the controls during that time. He probably wanted someone who could read check lists and operate the radio while he landed the plane.
That's what I thought; another set of eyes and hands to take care of the mundane stuff for him while he concentrated on flying.
Thanks for getting back to me.