If you look up ‘Faraday Cage’ you will see that the protection requires a continuous conductive surface that leads to a ground wire for discharging the ‘pulse’. Thus a car fails due to windows and lack of ground. The advice about safety from lightning remains valid as the car’s metal shell (Corvettes need not apply) is acting as a conductor and the strike will do a ‘spark gap’ jump to the ground.
Faraday bags and pouches are a shield for the contents and are limited to protecting more against detection than EMP. They are also limited by practicalities as higher protection (frequency ranges & power) needs bulkier shielding. Also a shield bag sufficient for reduced detection of cell phone will conversely make you unable to use that cell without removing it from said protection.
“If you look up ‘Faraday Cage’ you will see that the protection requires a continuous conductive surface that leads to a ground wire for discharging the ‘pulse’. Thus a car fails due to windows and lack of ground.”
Does not need a ground.