Yeah, he was in the very front line. How does he get in there and not get slaughtered? In fact, probably the silliest thing of the whole episode was where we see how overwhelming the zombies are in one scene, but later on, the guys (Brienne, Podrick, etc.) are fighting against hordes of zombies in hand to hand combat for extended periods of time, but somehow survive. Wasn't Samwell, with no skills or even weapons that I recall, sitting under a bunch of zombies for 10 or 15 minutes? Not exactly what you would have expected in seasons 2 or 3.