How can my friend find out if her late father has a life insurance policy?

My friend's father died recently. Twenty years ago, her father took out a small life insurance policy to pay for his funeral expenses. The beneficiary is my friend's stepmother. The stepmother doesn't even recall a life insurance policy. She wonders if he had cashed it out. How can my friend find out if a life insurance policy still exists? Those unclaimed fund sites don't usually include life insurance policies, and the life insurance company may not know that a death has occurred.