He put his arms up, but it hit him in the facemask, so, yeah, it was a lucky break. Sheesh.
Yeah, re-watch the play. There was lots of contact - as in Nelson hugging the DB to draw the penalty/try in vain to make his way back to the ball. I watched the entire game over last night, and I just watched the play in question on NFL Live. You're just...wrong. Watch it, then come back to me. It was a terrible call. Tim Hasselbeck (hardly the end-all, be-all of judgement calls, I know) even made a point of how bad of a call it was. It was a gift from some bad zebras.