dude just watch when Sayn woke up, he spend 2 minutes in the bedroom trying to hear what's going on outside, then went straight to the bathroom and was looking for some sign that something happened and found her hair.
He wouldn't have come out of the bathroom with a smirk on his face showing it to her like "i know your secret" if he didn't know.
He's just chosing not to go to war in the middle of the night