Seems likely to me that NSA found the server and imaged it. FBI's job was pretty easy after that.

Someone asking for help on the bitcointalk forum for a new venture? Happens almost daily. Someone asking a question on SO about how to access Tor? Ditto.

You don't discover who "Dread Pirate Roberts" is from this. But you do discover these types of things pretty easily AFTER the NSA tells you who DPR is.