My mother had a whole life insurance policy she used as collateral for a loan. She is now in hospice. How do I find out who the loan is with?

Do an online credit check for your mom, it should show all loans, credit cards and more.

insurance company is saying they don't know who the loan is with....we are trying to arrange burial plans for when she does pass but this is hindering us

The insurance company annual statement should state if there are loans against it. Usually the loaner is the insurance company itself. Once you send them the death certificate, they will deduct the loan from the payout.