Murfree couldn't have caught him. He didn't try, because he was trying so hard to rescue Bud Gregory's gadget, which Bud had used as a stepping-stone when he scrambled out of the car. Those are the two things that make Murfree mad. Bud Gregory fled and could not possibly be found. And his device was smashed so it wouldn't work any more.
Murfree still has it, of course, but he's lost all hope of understanding it. In fact, whenever he thinks about Bud Gregory he begins to swear. He envies Bud Gregory. Because Bud Gregory is something there isn't any word for.