To defeat stalkers, Apple included an alert to ping iPhones when AirTags were 'tracking' them. The victim (or thieves in this case) can find the AirTag as it will 'ping' while the alert is active. Disabling the speaker makes this much harder. I use a watertight black case to hold/hide it that looks anything like an AirTag and put it in an inaccessible spot. Can they find it.. maybe, but it would take a looooong time to do it. Can they turn off their bluetooth, yes. Can they drive it in a metal building far away from other phones/wi-fi, yes.
Better: I had an old iphone hidden in our van with a $5/month sim card in it. Hardwired the charge cable to the 12v hot. Use 'Find My iPhone' and turned off all notifications/noises on the phone. Worked great, luckily never had to use it. I did use it once when we got lost on a hike and had to find our way back, and it worked great. Lot's of the YouTubes out there that show how this works.
No measure is 100%, LoJacks are defeatable. AirTags are a pretty effective and cheap solution to track a car that doesn't rely on the Toyota software and doesn't have a monthly fee.
The Best: EOD Guy comes up with a DIY for a hidden fuel pump kill switch. That, or a dummy OBD port DIY. Pretty please!