Why Modiano should have ended Missing Person a few chapters earlier

Looking for a moment at the ending of Modiano's Missing Person: Don't you agree, whatever you may think of the novel up to this point, that Modiano carried the story just a chapter or 2 too far? Seems to me that he builds toward a fine conclusion: Over time, Guy, the narrator, regains at least pieces of his memory, and at last he has in his mind a clear account of the last days of his wife, Denise: they travel with three others (the English jockey, and another couple) to the border town of Megeve where they settle in for the winter, waiting for an opportunity to cross the border. Their companions become increasingly part of the social life of the village, which is risky - they should try to keep their profiles low. At last a Russian, who seems to be friendly, offers to convey Guy (using the name Pedro McEvoy) and Denise across the border into Switzerland. Foolishly, they split into two groups - and Guy/Pedro never sees Denise again. He survives somehow, we never know exactly how he gets back to the village in the middle of an Alpine blizzard, and from that point his memory is erased: to me, that's a perfect ending - disappearing into the whiteness. We understand that Denise is an analogue for all those obliterated by the Nazi Occupation and by their French collaborators and other opportunists. Strangely, though, Modiano opts to continue the story line for a few more chapters, w/ Guy seeeking out more information about the person who led them to this border crossing, and in a few very quick chapters he follows leads all the way to a South Pacific island where the trail goes cold. We don't need these chapters at all - and they completely break the noir, insular feeling of the novel - confined to the strange neighborhoods of Paris, most of them not changed since the war - with the "pastoral" alternative being Nice, where Guy's boss, Hutte, has retired and from where he provides via letter occasional updates about life in the sun of the South. (There are mysterious connections, too, between Hutte and some of the Russians in Paris - hinted at, like much in this novel, rather than dissected and developed.) Oddly, or perhaps it's not so odd, I had my own memory blackout and had completely forgotten the South Pacific chapters; would have sworn that the novel, which I first read about 2 years ago, ended in the snow on the Swiss border. Doesn't that tell you something?