The simple fact is that you did not have a valid driver's license, period. An additional driver may, as far as they're concerned, drive their car. You could not legally do so.

Could they, in theory, have a special contract for additional drivers who may only use the car when there's a licensed driver in it? Perhaps, but I doubt they do. I also doubt they'd want to, since they probably don't want their cars used for driver training (which is the usual learner's permit situation).

The above poster did not have a temporary license. He/she had an expired license from one state and a learner's permit from another. Those do not add up to a valid license.

Regarding temporary licenses, which most states now issue on renewal because they've gone to digital imaging systems: Suppose you renew your license every five years and have the temporary one for a week. That means one week out of 260 you have a temporary license. Since this is equally true of everyone else, one renter out of 260 on the average will have a temporary license. This translates to several renters a week at an active airport location, one every few weeks at a slow in-town agency. It's safe to say that nobody reading this post will be the first to show up at an agency with a temporary license. It happens often enough for every car rental company to know about them and accept them.