I left a GPS in a Hertz vehicle once. It was lost, but never found. Also, the process for tracking the case was unwieldy and extremely time consuming.
Here, though, I have to give an attaboy to Dollar in IND: I left a GPS in one of their vehicles, and when I landed after my flight, I had a voicemail from their lost and found manager who had proactively called me to ask what address I would like it sent to. They charged my credit card for the shipping, but as this was my screw up, I thought that was totally fair and reasonable.
Cheers,
Paul.