We need to see the original Notice to Keeper (NtK). Reminders are irrelevant.
Have you tried Plan A? Get the restaurant to get then PCN cancelled?
You need to edit your post because you have blabbed the identity of the driver. Only ever refer to the driver in the third person. Any response from you must only be as the Keeper.
If you never received the original NtK, then make a formal complaint to CEL and demand that they reissue it and that you require evidence, such as a proof of posting certificate, to confirm that it was sent as per the requirement of the PPSCoP section 8.1.2(e).