What works and what doesn't in Jonathan Lethem's NYer story

Over the years Jonathan Lethem has proved to be an accessible author who's really good at establishing a scene and mood (see Motherless Brooklyn) and at drawing on childhood memories and adolescent interests and passions (comic-book heroes, e.g.). I don't know hos work well enough to comment in any detail on his novels, but it does seem to me that he's better at establishing a premise than in building a traditional narrative arc, and that's pretty much what we see in his story in the current (OK, last week's) New Yorker, The Starlet Apartments. the story starts of well: He establishes the two main characters, the narrator (Sandy) and his college (or grad school?) buddy; they're both 3 years out of Yale, and the narrator is foundering, not really able to establish himself as a writer, when his friend invotes him out to LA where they can share an apartment and write scripts (and drink a lot and do lines of cocaine). Over the first part of the story, Lethem gives us a great sense of how these two guys set up meetings with producers and others trying to sell half-baked ideas and meeting w/ lots of encouragement but no $, a highly typical scenario. Eventually, he tells us that his friend will go on to a great career buying cheap and turning profits, and we can't help but think of Weinstein, though Weinstein was always rough around the edges and this guy is more hip and more East Coast establishment (Yale, qv). Setting well established, the plot kicks in when narrator's sister, Maddy, just out of college, flies wet to maybe live w/ these guys while establishing her own career; as we surmise from step one, the friend seduces Maddy and they disappear for a few days, which sends brother Sandy into a tailspin. Is he truly worried about her? Or just jealous? And jealous of whom? Eventually he finds her - they'd been shacked up on a vacant apartment in the same eponymous complex where the guys are renting - and she insists that he take her to LAX so she can fly home. Was she injured, abused, held captive? - she doesn't say, and to me that's the heart of the story and it just doesn't work to have her depart w/out any explanation or confrontation. It's in a sense a darker and displaced version of Jules and Jim, but with too much left unsaid and unexamined.