Figured I'd check up on the HTZ section today after a few months of break......

Here is my take, as a former HTZ employee and how it might go:
Your chance of being caught doing this would be small, but as you have seen, there are fairly serious issues if they do find that you are lying.
First, HTZ CSRs (checkin/pickup desk) employees will not generally care about this. While an overseas DL will probably give them a hang up, they ARE rated on numbers, and I think part of the evaluation involves speed (while still being complete),
Second, CSRs will probably just believe if you say you were in a country at that time, and will not demand proof of a ticket or something to show you were there (see #1 also)
Third, no manager or supervisor really wants to deal with crap like this. They do, but generally, there are other things they concern themselves with.
Fourth, and lastly, I doubt a manager would go that far to challenge you about facts like this. It would be offensive to tell a customer that you know they hadn't been to the country previously and booked the reservation overseas.