alt Hacker NewsIIRC, this indicates that it's linked to someone else's account, and has not been shared with you. The "beep when moved" feature is to alert people they're being tracked.
For example, I let my mother in law use luggage of mine with an airtag still in it and every time she moved it after the first day or so, it would play a noise.
I had the thought too, but there is no way anyone else could have gotten physical control over this and shouldn't I see that AirTag when I scan for things in my surrounding as an anti-tracking protection?