That's very strange, as usually if it has 1 side, it will have the other, but audi can be penny pinchers at times unless its a spec'd option for sides now.
Best option is to ping the existing glass out, plug the drivers glass into passengers, test the dimming circuit by putting tape over the light sensor on the outside of the windscreen, then torch onto the interior sensor on the rear view mirror, you may have to also put your finger over the other sensor that is on the back of the rear view mirror, this will tell you if the circuit is live on passenger side, if so, grab some glass & fit.