Untouched and out of range of all cellular networks (disregarding the SIM), most likely; we don’t know how long, though.
If your phone hasn’t connected to a cellular network in weeks and is locked in a stationary box 23.9 hours a day or more, then I’m not sure I would be surprised if it becomes automatically unreachable in this way eventually — it’s becoming unreachable any time it reboots for an overnight iOS update already, right? so an inactivity reboot isn’t going to have a worse impact than that already does.
(Note that physical SIMs were discontinued in late 2022 models, but it allows you to set an eSIM PIN with the same effect.)
If your phone hasn’t connected to a cellular network in weeks and is locked in a stationary box 23.9 hours a day or more, then I’m not sure I would be surprised if it becomes automatically unreachable in this way eventually — it’s becoming unreachable any time it reboots for an overnight iOS update already, right? so an inactivity reboot isn’t going to have a worse impact than that already does.
(Note that physical SIMs were discontinued in late 2022 models, but it allows you to set an eSIM PIN with the same effect.)