I'm not qualified to say if it was fake but if you had a Emerson CQC-13 and it was a collectors edition you'd
A) Have to be really desperate to sell it for cash
B) Seriously not have any friends on various blade forums especially considering you either are a member of ECA, OR you purchased the knife from a forum yourself. ...and then proceed to sell it on ebay, where EKI fakes are abound.
C) I'm going to have to reiterate #1, since you're selling it to just anybody with cash and not necessarily a good home.
He has no rep of selling knives, but his buyer feedback shows that he is indeed a knife hobbyist. Just message him for a picture of the lockup and that should speak a little more.