Although I'm not disputing the logic of that and Sloane could well have had a plan to find Nadia in mind, I am somewhat stumped as to why he would choose this route when it could so easily back-fire. Jack would know that Sloane wanted the info found out, and he could easily have taken it as flaunting the affair in Jack's face - and in telling someone else first, not 'fessing up. jack, for that matter, doesn't have an incentive to find Nadia, except perhaps to hurt her, and if he keeps Sydney from finding out, he could have done just that. Once Sydney finds out, of course, hurting Nadia goes out of the window - but Sloane is running a terrible, terrible risk. Does he actually know that Jack shot Irina? Because if he doesn't, she would be the logical choice for him to go to re: Nadia, not Jack, who has such a violent reaction to the news.

Also, the whole thing backfires massively, which, given that Sloane's plans don't normally do that, reinforce the impression of sloppiness.