The way it is framed in the film it doesn't make any sense at all. That's a huge leap of faith they're taking there, assuming that the audience would grasp the full details of the insinuation... The part with the army guys, you're right about that, hard to argue there, but what rumours would he possibly follow to make his way all the way to the diner up north? Once he gets there all of the scientists have just arrived, as did Lois. There's no indication of any previous occurrences in the area that may have led him there.