My mirrors popped out in this california heat wave after owning used m3 for a week lol

You should not be having this issue. I've owned my highland since april of 2024 and it's been baking here in the UAE heat since then and I've never had a heat related issue. Maybe your mirrors were not installed properly? Don't know if they're clipped in or glued on but I'm sure there's a way to fix em. Difficult to help without pics.