ECGC Claim on goods damaged in transit

We had exported one container load of granite to our client in USA on FOB basis after getting credit approval from ECGC on them.

Unfortunately the goods got damaged in transit and the client refused payment. Our client did not create any marine insurance for in transit of goods from India to USA.

Here ECGC says the transportation should have been insured, hence refused payment. But we were not responsible for insurance of goods as it was on FOB basis only. For fault of the buyer why we should be penalised.

Is It right? Please suggest a way out...