This sounds like every CL post ever btw.
This is all hypothetical, but it looks like one of you is stalking the other or both of you are stalking each other. Also I know nothing of Sarah and her plan, but he probably searched for that before talking to you.
Furthermore, I have to say that this is a great job playing the devil's advocate. Congrats!
He knows you well through either letters or searching on the Internet or using a background check. The bits and pieces that imply that you know him are what he gathered online.
The prettiest little liar there ever could be.
Heads up, BFFs!
It's open season on liars and I'm hunting! - A