It would be safe to assume that Gordon was a resident of purgatory since he died a vampire. So that also means that he was one of the souls that was absorbed by Castiel.
Gordon the Hypocrite
Am I the only one who thinks that Gordon was a complete hypocrite in his last appearance?
All that talk about how he couldn't control the evil inside him, and in the end, I think he just used himself as 'evidence' to himself that Sam was going to go evil because HE automatically started killing people...