now seriously if the person suffer some kind of accident that causes some partial temporary disfiguration like being bruise and heavely swollen then they won't be able to use their phone if they have face id on, until their face go back to normal, but what about a permanent disfiguration like a car accident that changes the shape of your face or your head. what about drastically burning your face, you can call apple but i'm sure they are not going to help, the only way to access your data is if you have it in you iCloud drive then you can use your mac or any other device to access that data using your apple id, but if you have 2SA or 2FA enable in the device that has face id enable then how can you allow the other device to access you account, unless by some miracle you already gave permission to that device before, if you clean your history in safari then you have to the whole process again. allow and trust