"My son's A&E visit"

My son is 18. I attended A&E with him with his GP's referral letter because he had developed a lump on his neck. He has moderate learning difficulties and a long-term chronic health issue. He would not have been able to manage on his own as the very first task was to complete a quite complicated form confirming his right to treatment in the UK. After a reasonable wait, we saw the triage nurse. They did not introduce themselves to me. I'm not sure that they introduced themselves to my son either. They discussed with my son in my presence the fact that he would be referred to the ENT duty doctor. I provided background history. All of a sudden, they looked at me and said 'And who are you?' My son is black and I am white. He is my adopted son so I am used to a disconnect where people assume that we are not related. But one point that occurred to me is that he is 18 and therefore surely can have anyone in attendance. I informed the nurse that I was the father. They did not comment. I felt very uncomfortable because of the way that they said 'And who are you?' as though I was up to no good. It's a shame because I personally have had good experience of this hospital. We have two further visits in the coming weeks so I hope that this issue does not repeat itself. I need to be present as my son will not pick up on important detail and will frequently misunderstand instructions or information.