re: 2 story window over our stairs just popped and shattered.

We had the same thing happen 3 weeks ago on an entry door. There was no bird laying near it, no rock or debris, the door is over 40 yards from any point where the neighbor would be moving and at an angle that would be almost impossible to be hit by a rock from his mower.
Outer glass shattered but never fell out, the glass pane was about 65” tall and about 26” wide and a custom design door so not just a rectangle, the best replacement price was $1150.00 so you’ll be out a little chunk of change. The glass guy said it was most likely from variations in thermal expansion, it was 68 inside and 104 outside, but that hasn’t broken any of my other doors or windows. He said the doors don’t have nitrogen or any kind of gas except air that’s trapped between them when the manufacturer lays the 2 sides together.