The contract the renter signed would be what matters and I can assure you Hertz has a tight contract on discount codes and eligibility.

It wouldn't really matter what the person handling the return does; it will be sent over to their claims team (internal or external) and they will validate the entire rental, including any insurance options/liability options. IBM, almost guaranteed, will not pay for any damages as self insured either.

The only questionable part is the LIS, which the insured paid for, which would cover the other person's car and any medical issues to the other party. The OP did not purchase LDW, they purchased LIS which is for liability only and offers no protection to the rented car.