If this guy didn't believe in GOD before, do you suppose he believes now?
My guess, if he didn't believe in GOD before, then he is more than likely a rationalist and does not believe in GOD now...why should he? There are people who believe in GOD who die in car wrecks every day, so there is no empiric evidence to prove that one's belief or nonbelief makes them prone to missing death by car wreck. Plain and simple, he got lucky -- and I'm sure he knows that. Quite frankly, I'm sure he's more apt to believe in traveling at a lower speed and paying more attention to the road right now, than he is apt to believe in GOD.
Now, I know, being as I am a former believer, that pictures like these are strong faith affirming sorts of things to those who believe. Perhaps you don't understand how someone who doesn't believe can persist in their disbelief after seeing such a faith affirming picture. All I can say is, there are pretty believable pictures of Santa Claus on the internet, (plus there's that tracking site on the internet to give more "proof" to the evidence of there being a Santa Claus), but would those things change your disbelief in Santa Claus?
Also, who is to say that the GOD who, hypothetically gave the driver of the truck a second chance, is the one you believe in? Who is to say it's the Biblical GOD/(G_d), or Zeus, or Thor, or Guan-Yu, or the Flying Spaghetti monster? (You're an atheist, too...you just deny one less god than I do.)