To me, the more interesting question is how another person took your Gold car at PDX from the Hertz lot roughly an hour before your arrival. Apparently the employee at the gate didn't look at the driver's license carefully or it was an inside job. Fortunately the vehicle wasn't damaged, stolen, or abandoned. However, it's a bit surprising that Hertz IT didn't detect that "you" had rented two vehicles at the same time, presumably as the sole driver. Also, when you didn't see your name on the Gold board, the fact that "you" had already left the lot in "your" car should have been discovered rather than Hertz just finding another car for you.

Or maybe the second car wasn't really rented by someone else and simply represents fraud by the Hertz agency in question.