Chatterbox was unable to obtain details of this story, but Murph Murphy is the person to whom Edward H. Heinemann, an aircraft designer and engineer for Douglas Aircraft in the 1940s and '50s, attributes Murphy's Law in his (Heinemann's) 1980 autobiography, Ed  Combat Aircraft Designer . Chatterbox got the poop on Murph Murphy from Fred Johnsen, the historian at the Edwards Air Force Flight Test Center.
As far as the details go, Chatterbox wasn't able to confirm them.