Please help

I'm very disappointed of the service and treatment we received today while having lunch with my friend a male waiter come to clear our table took my phone and went missing ever since and the phone is not even two weeks old,when we asked he denied everything we asked if we could see the cctv footage we were told they have cameras,the manager went on to confirm that this is not the first time something like this happens in their store and nothever gets done about it