one of them's ??

A headline in my local newspaper: "Men threatened with gun while working on one of them's car." (I don't know how long the link will remain active.)

I can imagine "one of them's" as a contraction for "one of them is" or "one of them has." But as a possessive?

UPDATE: The link still works, but the newspaper has changed the headline to "one of their cars." Some might say this implies the men owned the cars collectively--I'm not sure about that--but in any case it's much better.

Elektratig picked up on this posting, as did Pillage Idiot (which has a screenshot of the original, in all its glory).