reference to Grothendieck and n-categories?

There will be a conference in Paris to celebrate the 80th birhday of Alexander Grothendieck http://www.ihes.fr/jsp/site/Portal.jsp?document_id=1661&portlet_id=14 and the publication of Pursuing Stacks and the associated correspondence will be announced. There is from my point of view one lacuna which I would like to fill. My memory is that I read in 1982 in a SLNM paper on category theory, I think by Jack Duskin, in which he referred to Grothendieck's interest in n-categories. This suggested to me to write to Grothendieck with lots of papers and asking for a meeting, since I was going to Marseilles-Luminy that summer. I have been unable to identify this paper. Help would be appreciated! Ronnie