Per MLBTR. (Insert mock outrage here.)
UPDATE by Charlie: To flesh this out a bit, as Grumbly does in the comments, the Pirates acquired Gaby Sanchez and Kyle Kaminska for a comp pick and Gorkys Hernandez. Then they traded Kaminska for Zach Stewart. Then they let Stewart go for nothing. Mostly what this suggests is that the Pirates really didn't think highly of any of the players involved, except perhaps Sanchez. In the end, I'd simply prefer to take all those transactions back and keep the comp pick, but that ship sailed months ago. Anyway, Stewart wasn't even in the conversation for 2013 rotation options, and losing him really shouldn't matter much.