What it means
Offline Device Lock is a supported Android theft feature that can automatically lock an unlocked phone after it has been offline for a period. Airplane mode is merely one way connectivity might stop; a user can also lose signal. Google says the phone must be unlocked when connectivity is lost and limits this automatic lock to twice in 24 hours. The feature does not make an offline device remotely reachable.
A real-world example
A stolen phone is put into airplane mode. The owner cannot see a new location in Find Hub, but a configured Offline Device Lock may later close the unlocked screen. A short voluntary offline test may not trigger it immediately.
What to do
Turn the feature on before a loss, maintain a strong PIN and know how to reach Find Hub and the carrier. Treat a remote lock request as pending until the device reconnects.
The distinction that matters
No instant lock does not necessarily mean the setting is broken. Offline Device Lock does not disable radios, recover the phone or protect information seen before activation. The exact availability depends on model and Android version. It should be combined with a normal short screen timeout and manual power-button locking; those protect ordinary moments before any theft-specific trigger is recognized.
Google Offline Device Lock
