Is it routine for the ER to apply for aid of a patient if insurance status is unknown?

My mom was admitted to ER after a motorcycle accident, I was told that she was not responsive at the scene or in ER, she later that night passed away. I recieved a letter stating that a application for aid was not completed on the date of services and that she was denied because of being uncomplete. Is this something that the hospitials do routinely or does the patient have to agree to the application?