What if the only computer (or even the only Apple computer) a user has is an iphone, and someone swipes it?
Surely in that case you're now locked out of literally everything, no?
Please explain to me why this is stupid because I'm certain someone thought of this very early on.
If you still can log in to iCloud, you're fine.
If your Apple ID password has been changed, Apple provides a workflow to regain access to your Apple ID [1].
There's also a process for account recovery for situations where you can't access your Apple ID because of two-factor authentication [2].
[1] https://iforgot.apple.com [2] https://support.apple.com/en-us/HT204921