[GTL]

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Moss lived close by. Chigurh seems like the type to at least troll through the neighboring towns until that transponder hit. But, I could possibly be nitty here.

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Moss didn't live that close by. It is unclear whether Chigurh would have found Moss via the transponder if Moss hadn't gone back to the scene. Moss wasn't just going to sit in his trailer with the satchel on top of his bed. He was leaving no matter what.

However, this isn't that important. You don't need to be so rational here. The bottom line is, Moss' fate is sealed when Chigurh finds out his identity. Chigurh finds out Moss' identity because Moss went back to the scene to bring water to the Mexican. Both the Coen's and McCarthy are trying to make a thematic point here. The Coen's hinted at the importance of this in their Charlie Rose interview, and McCarthy highlights it in the book by comparing Moss to Bell (Bell left some of his men to die in WWII)

It doesn't matter that Chigurh might have found him even if he didn't go back. He did go back, and that is why he died.