"Unknown accessory detected near you" on iPhone

While I was traveling by car, alone, on Friday night I got a notification "Unknown Accessory Detected" - "This item has been moving with you for a while. The owner can see its location." When I clicked through, it said "Your current location can be seen by the owner of this item"

It followed me across the state and into the next state.

It was really late when I arrived at my destination, and I was creeped out and didn't have enough personal bandwidth to try and work out how to address whatever was happening. When I woke up in the morning I figured out I could disable it, I tried to disable it and it said "Unable to connect to server. Please try again later." I haven't gotten another notification since then.

I didn't interact with anyone on my trip, I didn't notice any vehicle traveling super close to me for long amounts of time.

When I called apple support, they didn't really have any practical advice other than look for an unknown airtag on your car, and if you see the notification again, disable the device right away.

Is there anything else that could give this "unknown accessory detected" notification? This felt invasive and creepy, and I really don't want it to happen again, I'd rather just get it figured out, rather than wait to get another weird notification. Any advice or thoughts feels helpful, thank you in advance!

[Re-Titled by Moderator]