What a silly discussion.  Hayek's source was Hayek:  
  
"In the natural sciences, we .. have learned   
that the interaction of different tendencies may  
produce what we call an _ORDER_, without any mind  
of our own kind regulating it.  But we still refuse  
to recognize that the _SPONTANEOUS_ interplay of  
the actions of individuals may produce something which  
is not the deliberate object of their actions but an  
organism in which every part performs a necessary  
function for the continuance of the whole, without any  
human mind having devised it."  
  
-- F. A. Hayek, "The Trend of Economic Thinking",   
Inaugural Lecture delivered to the L.S.E on March 1, 1933.  
  
So Hayek was already using the language and notion of "spontaneous   
order" as early as 1933 -- _without_ having derived the exact  
phrase "spontaneous order" from anywhere.  The language was already  
in his vocabulary, and the idea was already in his work.  The only  
thing missing here is the exact phrase combination "spontaneous order"  
To repeat, the idea is here, the very words are here -- all Hayek   
needs to do is type them together.    
  
It's worth noting that Hayek himself makes it rather clear that   
his own original understanding of "spontaneous order" (the idea not  
the words) in social theory derived from Carl Menger, most particularly   
Menger's _Untersuchungen_.  
  
Greg Ransom