2012 Audi A3 Rearview Mirror/Rain Sensor

[moon_fury]

Recently purchased a 2012 audi A3 8p, and upon inspection noticed the rain sensor hanging down by the mirror.   I assumed an easy fix, get a new gel pad, re-stick to windshield.  

But after removing the mirror, the spot where the sensor is supposed to go has a metal knob that doesn't allow it to fit.   It appears to have the correct trim, and the black circle on the windshield etc, which is confusing.   Does it mean that this is possibly a wrong windshield?  Maybe for a car that doesn't have the sensor?   I'm tempted to just stick it off to the side, but it will look tacky/incomplete. 

Hopefully that makes sense, please see pics.  

[cliffcoggin]

My guess is that the mirror has been changed for a housing not designed for the rain sensor.