I found video. Turns out -- as often happens -- the video was different from how I remember it. The batter wasn't really "bailing out" as I said -- he took a step back with his front foot, but then steps back toward the plate when he realizes time won't be granted. It's at about 1:00 of this video. (What the video doesn't show, interestingly, is that the 2B U called the balk too, a split second before the PU.) I don't think there's any question that the actions of the hitter caused the pitcher to hesitate, but seeing the replay, I'm not sure the crew had a choice.
Baseball Video Highlights & Clips | 06.29.09: Ethier, Dodgers walk off on the Rockies - Video | dodgers.com: Multimedia