From the looks of it, it doesn't seem like Simba was following the path Nala used to escape the Pride Lands that led her to the jungle. While the jungle doesn't have a specific geography, one end of the jungle was surrounded by a thoroughly green plain, while another end leads out to a plain with brownish grass which is where Pumbaa spotted Nala (or should I say, Nala spotted Pumbaa).
Not to mention, at that point, Nala's scent is all over the jungle given how long she's been there since they reunited.
