I've walked away with the fob before. I'd do this in LAS all the time. I'd pick my vehicle, lock it (this is the key difference I guess), and go to the gold desk to get the damage form so I can fill it out at my leisure instead of feeling rushed trying to do it at the exit gate. (Interestingly, some gold desks in other airports wouldn't give me the form. PHL and ATL told me I have to do that all at the gate). When adding drivers, sometimes I've just done it at gold desk if there's no one there (plus I can see if contract has right price. I've had them screw up price in LAS and then I have to drive back around and go to gold desk to fix the mess up).

On another note, I had no idea there was a way to scan in the app like OP did. Obviously this was a big mess but I also agree that the OP needs to straighten it out with Hertz least they wind up on the DNR list. They might not want to use Hertz again after that experience, but in personally would not want to be on any DNR list. Never know if Hertz, thrifty or dollar might be only rental available or only reasonably priced rental available at some point in the future.