Everything gets torrented. The Humble Bundle got torrented and you could buy it for five cents. Complaining about something ending up on the Pirate Bay is like complaining about used book sales; you can't say you didn't expect it.
Now, if he could prove it cost him any sales, he'd have something novel. If he could prove that fewer people paid because he didn't include DRM I would be shocked. It's mere existence on a torrent network simply says that not everyone is going to do what strangers tell them on the internet.
