thanks for the tips and recs here.
blew a couple hours i'll never get back on this.
the laissez faire responses got me frustrated. Told them to find where the car is and close my bill. some manager said she'd take care of it. I asked, "how will you know when it was dropped off". she replies, " we have our ways". I say, "why don't you use those "ways" to validate a car was not returned before you start with the threatening voicemails!?"
anyways, 1 week after the car was actually dropped off, I get a receipt saying the car was checked in ~10 hours after i dropped it off. aaannnnd, of course, the miles used was listed at ~75 miles more than I dropped it off at. This triggered 75mi * 75c charge.
Hertz MCO needs to get their act together.