Yeah, that's weird. Since that person couldn't find the thread either, it does suggest that it's either removed or never existed (and bear in mind that moderators do remove threads which they feel malign surgeons in an actionable way). I would think that if it were happening, I'd at least have *heard* about it while I was chatting with everyone there. And the porn star would be easy enough to chase down if they truly did want to enforce such a thing, so if she's really out there, I agree with you that the NDA is probably fantasy.
(But again, I can't call someone else a liar for sure, I can only say I never saw a hint of this NDA thing.)