If you car has been evolved in a serious accident and the insurance company are likely to settle the claim as a total loss i.e. it isn’t economically viable to repair the vehicle. The private number plate is officially part of the vehicle. Therefore Unless you arrange with the insurance company to transfer the DVLA number plates or retain it on a V317 retention certificate, the number may be lost.
If the car registration number is lost you could write to the DVLA explaining the situation together with a letter from your insurance company stating they have no interest or claim in the DVLA number plates. They may take a sympaphetic view and let you have it back, our advice would be not to take that chance and have the number removed from the one being written off.