This solution also works:
* if you’re this paranoid, do not give your phone to a stranger
* if you’re this paranoid, do not give your phone to a stranger
To be honest. At the moment a device of any kind is left unattended accessible for others security is already violated. Ability for physical manipulation allows for literally everything - same status as harmful software.
Because I’m not paranoid enough I hope for the best and rely on the login and hardware encryption. Or here on a nickname :)
Anyway. It is a valid use case well handled by Apple and Google in the past. They designed the lock screen for this.