Looks like if the guy has an air tag app he can find yours. All he needs to do is add his and tag your car as his as it moves away he'll be alerted yours is tracking him.
AirTag is designed to discourage unwanted tracking. If someone else’s AirTag finds its way into your stuff, your iPhone will notice it’s traveling with you and send you an alert. After a while, if you still haven’t found it, the AirTag will start playing a sound to let you know it’s there.
There is no Air Tag app....Its Find My Friends app on an Iphone....the Air Tag is paired only to owners phone not seen by others.....same process for locating a family member is same app....no one else sees your family members location
Sort of but if you leave something far away, the Apple Big Brother spy network can find it, ping the location to iCloud and notify you where it is on a map.
If someone stole your car and had an iPhone, they would also be alerted there is an Airtag if they are part of the network
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https://www.apple.com/airtag/"When youʼve left something far behind, like at the beach or the gym, the Find My network — hundreds of millions of iPhone, iPad, and Mac devices around the world — helps track down your AirTag. And itʼs designed to protect your privacy every step of the way.
Your AirTag sends out a secure Bluetooth signal that can be detected by nearby devices in the Find My network. These devices send the location of your AirTag to iCloud — then you can go to the Find My app and see it on a map. The whole process is anonymous and encrypted to protect your privacy. And itʼs efficient, so thereʼs no need to worry about battery life or data usage."