stalin made the same mistake in dealing with evil that everyone makes: you think you can cut a deal. Hitler proved himself totally and utterly ruthless. stalin proved himself too clever by half, he figured no one could be a bigger evil genius than himself, but he was wrong. he must of thought that hitler was like the other western leaders he knew.
as far as i know the its never been proven the two actually met, although there is some rumour i believe that they did briefly.
I would write that off as rumor honestly. Hitler's movements, even his secret ones, were well documented by the Germans and most of Germany's official papers were captured after the war. I would bet that it would be documented very clearly if that ever happened.
On top of that, Stalin was never an easy person to meet anyway since he was so paranoid. I know the Ribbentrop met him, but I not sure if even any of the British or French diplomats met him directly in 1939 during these negotiations. (I could be wrong on that last point).