I can't for the life of me find a story I read not long ago, online somewhere.

The plot concerns two girls. They were lured into being paid subs, and one disappeared/never came back/something like that. The other girl arranged with the manager of the agency to be sent in after her, to effect some kind of rescue. She was subjected to tortures, as she had been sent under the pretext of being the ultimate pain-slut... After a while she begged release and admitted that she was just looking for her friend, at which point her captor said 'I know......'

Anyone know where I read this?? It could even have been on this site, but I don't think so...