It would be both confidentiality and to protect the patient. You said you were friends, but they only have your word for that. It's a sad fact that they have to err on the side of caution, but it is true.
I was with a friend at her house when an ambulance was needed and they still asked the patient if she was OK with me being there and going to the hospital with her as although I was her carer and she was mine, we weren't next of kin and we didn't live at the same address. They took my details and listed me, with my friends consent, as her carer.
Keep being a good neighbour and friend. As others have said, see if you can have the sons telephone number so you have a contact should one be needed.