Who leaves 10K worth of anything in their car? I get antsy leaving my $200 laptop hidden under my seat! This person is crazy. There is also no guarantee they person who stole the bag wouldn't dump the bag(with the hidden AirTag) and just keep the gear or that the police would help recover it even if you gave them the location(many times the don't).
It's not very risky to leave expensive items in the car, but in the trunk, not on the backseat! Also, never put these expensive items or really any kind of bag in the trunk after you park. Always do it before the ride. Or at least make very sure that no one is watching you. This is a basic safety drill. And it doesn't apply to expensive things only. You don't want your window broken for a sport bag with a sweaty t-sh…
A frustrating thing is that it's completely optional to live in a society where this is a problem. We know how to stop this from happening. There are places where you just don't have to live in fear of some low-life breaking your window, and we have the technical ability to replicate those conditions in any moderately-wealthy country, if we aren't prevented from doing so.