you did not get the tricky pt

here.

The rental car company refused to give them contract copy, claiming they shredded the copy - who knows whether it is true or not ?

The OP does not sound he wants to sue rental car company - it sounds to me he wants to claim the money he paid car rental company from his insurance company - but without the copy of the contract, he cannot provide proof to his car insurance company. therefore he wants to get a copy from the rental car company who refused to cooperate.

It is hard to explain fully all the intricacies may have involved here, unless you are familiar with car insurance (your own car, comprehensive) and what is involved with rental car etc.

Your thinking is too straight forward without the "American Way of handling business" (all legal, by the way). There is no right or wrong, just the way things are handled in this country.