Send it back to Glock. I would be shocked if they didn't take care of you. The mass of that firing pin should not be able to break that gun. There had to be a defect in it. Did you pull the rear plate off and inspect the firing pin? I would be interested to see what that looks like.
Even if this happened to me personally, I wouldn't bother with a snap cap. This would have happened eventually in a real fire situation, and it could have been worse - if not more complicated a warranty issue. The fact that no ammo is involved makes it a slam dunk warranty claim. Not that I think glock would have given you trouble otherwise. After reading a whole book on Glocks recently, their profit margin is so high that it's a no brainer to just replace it.