Killah, didnt you mention in the original thread that Dude brought home drunk office chick and also another male friend? Maybe that male friend knew what was going on? Maybe he hinted at it to someone who in turn told your ex? Or maybe he told your ex himself or told her the story of that night and how he and the drunk chick ended up at your crib. The ex could easily infer just from those minute details that you and the drunk chick went at it.