This happened to my wife’s friend’s son, just yesterday. He lives with his parents but is engaged and in the process of moving out.
He bought a used car from a car dealer out-of-town (about an hour and a half away). He paid $21K (the dealer claimed to have bought it for $18K from a guy he met in a diner). The dealer insisted on being paid in cash.
As he was driving it home, his iPhone kept on alerting him that there was a tracking device in the car (or vicinity). But he couldn’t find on. When he got home he spent a couple of hours looking for it, and finally found it. This freaked him out and his father parked other cars close alongside it in the family driveway, to block off access to the car. He kept on checking on it from time to time as well. But then, 10 minutes after the most recent check, he looked out and it was gone.
Of course, the fact that the dealer insisted on being paid in cash made him Suspect #1. (He claims he will reimburse for the car, which is itself weird in any event, and I wouldn’t hold my breath based on a promise like that from a used car dealer.) But I don’t know. It might be crooks targeting the guy’s lot.
My wife googled around and found any number of articles about car thefts of this sort, e.g. AirTags are being blamed for luxury car thefts, but it’s not a problem unique to Apple - 9to5Mac