[rezonant]

> The Waymo passenger answered and there was much giggling. She kept saying she didn't know what to do. I said just leave it in the car.

I inferred that you discussed this with the person, since you indicated you talked to them via voice. That would have been the perfect time to arrange for return of the device.

I guess after reading between the lines, this person didn't suggest this action during the voice call, only via the text you discovered afterwards?

Elsewhere you mention that leaving the phone in the car was the best course of action, but the next person in that waymo could easily have swiped it.

I suppose a middle ground could have been to tell them to put it in the back seat pocket or something so that it was a bit more hidden while you contacted waymo support to let them know to retrieve it.

> Also, tell me more about how a stranger holding a random found device authenticates a caller as the owner of said device.

This is a little much. That's quite a threat model you are operating under. It explains why you immediately wiped. I think most people are not concerned with that contingency.