Car stolen, bureaucracy question

On Christmas day my car was stolen. Immediately reported to the police and got the insurance papers for the claim. The insurance requests the car to be de-registered (Bitte melden Sie das Fahrzeug ab!).

In Germany, in order to de-register a car, one needs a code that is hidden under a sticker on the "Zulassungsbescheinigung Teil I". Since the document was in the car and the car was stolen, I can't peel of the sticker and access the code. So I am left with having to take an appointment with "Zulassungsbehörde". Unfortunately my local Zulassungsbehörde (Berlin) has a slot only in 2 months.

Aside from the kafkian loophole (police knows that my car was stolen, why isn't the car automatically de-registered), is there any other way to speed up the process?

Thanks

edit: eventually managed to talk to the Zulassungsbehörde and got an appointment next week!