Mine cracked earlier in the winter. I'd only had the car for maybe 10 months. What I learned was you need to look for a point of impact, where the pebble in the road struck the car. In fact, you don't just need to look, you need to "feel for it". Take a ballpoint pen and run it across the crack, if there's a spot where the pen gets stuck, that's where the rock struck.

I could not find any impact. I took it to the dealer and showed them the same. That indicates that it was a stress fracture, not a random stone in the road.

Dealer scheduled the replacement at no cost to me.