Can it be Gossamer Empyrean by opt_destiel? Summary: A hunt dealing with missing persons quickly leads to an elaborate plan in a desperate attempt to prevent what is happening and possibly save one of the kidnapped children. The only problem? Dean isn't at all enamored with the role that he has to play. He'd rather be doing something other than playing Castiel's sex slave and looking pretty.

http://otp-destiel.livejournal.com/70017.html