User blog comment:IamJakuhoRaikoben/Chapter 386: Galaxia Blade, Review./@comment-2214433-20140530083913/@comment-7418318-20140530114444

And there's another small ray of hope. There's a way to explain Gray's shocked face even without him recognizing Silver's face.

Maybe he recognized the feeling of Silver's magic and thus realized that this is the person who froze over an entire village, dozens of Giants and the Eternal Flame. To face someone who could do all this is a quite scary thought. And to make matters worse, even though Gray doesn't know that yet, Silver also froze Natsu solid before he could even blink.