Rogue One wrote:
Most likely just a weak point in the glass that finally failed due to the temperature changes.
I agree here.
I highly doubt that Infiniti uses tempered glass in those mirrors, unlike in the windshield, windows, and other exterior glass.
I'm hoping that your servicing dealership has stellar service and will accept the job as a warranty item. I have a feeling that if the dealer is going to do the fix, they'll end up changing out the entire sun visor assembly on that side.
For an alternative solution, a glass shop may be able to cut you a piece that'll fit in there; but it might not be worth the hassle to pick the sun visor apart and reassemble it. Since it looks like you'll be getting this fixed either way, you can always try this first if: 1)this won't be covered by your dealer; 2) you have the time; and 3) you're both handy and patient.
Please let us know the outcome. Now that you mentioned this, I think I should go check my mirrors too

.