Another thought -- the comment earlier about how they met -- I forget the source -- said PF helped KB move from WA to CO.
So in addition to his own experiences and contacts in the ID area, PF also has his experiences passing through (not necessarily that part of ID, but possibly, we don't know) with KB herself. Either both in the same car or possibly caravaning in separate vehicles. He may have heard her anecdotes about her previous passes through the area, etc. I hope LE is asking her family for any of those anecdotes they can think of, in case they might be clues to his actions.
Or, even better, let's just have LE have already found all the important evidence in Twin Falls and are getting ready to report on it in a few hours.