Have you ever had your rear view mirror fall off? Mine did about 2 weeks ago, and low and behold no one knew how it happened. Regardless of how it fell off, let me tell you about something to repair it.
My husband and I went to O'Riely's here in town and found a product by Permatex. It is made specifically for rear view mirrors, a professional strength adhesive that is ODC free. It claims to permanently bond the mirror bracket to the windshield. The windshield glass is different than most any other glass, it is exposed to the direct hot sun, to rain, snow and sleet, and extreme cold temperatures, so you really want to buy the right adhesive.
It is simple to use and comes with everything you need but a straight razor to clean the previous adhesive. You get a towelette that cleans and activates the adhesive, and it takes only one drop to secure the mirror firmly where it needs to be.
Be sure and read the directions before using, I think you will be as pleased as I have been, and it is guaranteed to work!