I had someone take my rental car from Avis in SFO - not when I was in it; my flight was delayed, and I didn't end up picking up the car. I had called to cancel the reservation once the delays started stacking up, and they confirmed that, but ended up giving the car to someone else anyway. Once the charge posted, I fought it with Avis repeatedly (even showing that I was in the air on the way to SFO from across the country around 40 minutes after the car was driven away), but they never reversed the charge, despite multiple agents saying they were going to do so. Next step, I disputed it with my CC (Chase), and so the next part of my saga will now probably be relevant to you....

The CC dispute was easy; they looked at the evidence and reversed the charge. But it turns out that had two consequences. First of all, I went to pick up a rental car from Budget about 6 months later on a holiday weekend in a tiny airport, which I was able to book under my profile just fine, only to get to the front of the line (fastrack wasn't functional at that airport) and find that my reservation was cancelled, and I was blacklisted "forever" from all future rentals from any Avis-affiliated company (I've appealed that, but never heard anything back from any postal or email address, so I assume it still stands). Almost all rental cars were gone from that airport, and I had to drive 2.5 hours to my destination, with no public transit options - it was a nightmare.

Secondly, Avis sent my account to collections. I had to dispute that with both the collections agency (who were also super-reasonable about it, and handled it very professionally) and the credit agencies due to the hit to my credit rating (again, this was fixable, but it was all just a tremendous pain in the neck).

So, sorry to be the bearer of bad news, but you might have more headache in your future. I hope Hertz acts differently than Avis, but I doubt it.