[Pattyk1978]

Is it just the flat mirror itself or the whole side rear view mirror housing and all?

If it's just the mirror, I think you may be able to just pop it back in. Just push it in with pressure on the center of the the mirror, preferably with a towel or gloves to prevent fingerprints.

According to this, popping out the mirror is as easy as getting something in between the housing and mirror to pry it out so I would assume that you can just push it back in. Just don't force it if it feels like you are pushing too hard.

https://www.kioptima.com/power_door_mirror_actuator-774.html

It's the whole housing unit folded them in when we got snow here and then unfolded the mirror and it came off