Keys in the mailbox of the workshop = theft

Our Avensis T27 2009 Exe was stolen. Keys were thrown into the mailbox of the workshop and the next morning the key with the car was gone. The car is fully cascade insured at the HUK24. Our behavior is grossly negligent. The insurance includes gross negligence, but not in case of theft. What do I have to reckon with? Does the insurance pay nothing? We cut the amount?