I'm sorry. I'm having trouble thinking it was hit by something, with a glancing blow (closed sunroof), hard enough to break tempered glass. Especially since she didn't hear impact, but DID hear increased wind noise. It would be a pretty freak accident, at best! An auto glass expert can tell if an impact created the break, as it would leave an indication at the impact point. A call to any reputable auto glass company will help. If they don't see an impact point, a call to Lexus might save you (or your insurance company) more than $800. If they do see an impact point, what have you lost? I would think it a good use of time to look into it. Besides, wouldn't Lexus WANT to know?

I'm almost positive I've read on this forum where Lexus has replaced original windshields that broke due to stress. Why not a sunroof?

 

I would think it is most likely from body flex after driving over a bump or uneven pavement coupled with the cold temperature. A freak occurrence but it happens. I had a rear drivers side window shatter driving down a bumpy Interstate with no other vehicles near me. I thought I had been shot at.

I had the motor go on a Highlander sunroof and I was told it would cost $800 just to replace the motor. So glass and a motor would run upward of $1600? I wish the sunroof was just an option, I hardly ever use it.

 

Happened to a friends Acura TL. No snow, no cold or extreme temperatures. The dealership said something got inside the mechanism and lodged in it, most likely when it was open a prior time, and when she pressed the button to open it this time, it shattered the glass. Foreign object.