My rear view mirror undid itself!
The screw that connects the ball, to the bracket on the screen, undid itself.

The ball itself is tight in the socket in the mirror...

How do I get access to tighten it back up?

There is a screw that you access through that hole in the bottom of that L shaped piece.

I've had to tighten mine once. But yours looks a little strange. Not sure what is going on there.

The base is missing(the part that attaches to the glass). The access hole in the arm is for the screw that attaches the arm to the base. The arm to socket attachment point can be a permanent fix (carefully glue... as to not get glue into the ball & socket)

hi
the part that attaches to the glass, is actually still attached to the glass

I read somewhere that I could try to prise the ball from the socket, but I am almost certain this would destroy it.
It looks like when it was made, that the glass might have been the last thing to go in and appears as if it is glued in.

Which all means I will either destroy it while trying to remove the ball from the socket, or perhaps I should create a hole on the back of the mirror, to attempt to access the screw...

thoughts?

That piece "pops" in and out. When I say "pops" I use that term liberally. The amount of force that is required to attach or remove it is scary. And I don't know what you'd grab that piece with since it has separated. A soak in boiling water helps but you'll need gloves. I didn't force mine back in until I bought another one. At that point I said "What the Hell" and tried it anyway, thinking it would break. It didn't break and I sold it later.