Seems like all he had to do was to show the receipt, the cops called the rental place, cleared the stolen car alert. The car rental should probably be charged for falsify reporting the car as stolen. And as the police said, you could probably ask for a year of free rental for the inconvenience.
The police has to take some precaution because they risk their lives walking up to a stolen car, thus the not so friendly tone and hand-cups.
There would be no story to tell had the cops been able to just call Hertz in a reasonable time. Instead apparently it took ages to go through the meanders of phone support.