okay, then he has no hope of collecting from anyone except Enterprise or the driver himself. It does not change the recommendation to contact the driver as the responsible party. And there remains a decent chance that Enterprise can and will step away due to rental contract violation.

It is a bad situation and the OP is likely stuck. I just wanted to cover all his possible options to get out of it and "timely filing" coverage denials are a real things so I wanted to be sure the OP was aware of them. It is insurance esoterica that many people are not aware of until it bites them.