"Partner admitted by ambulance with head injury"

My partner was admitted at 5 PM after a nasty blow to the head. The paramedics were amazing. I left the hospital at 12pm and at 1pm he called to say he had been discharged. We are not from England and when I went to collect him he was wondering around the car park confused. He had no discharge notes , nothing to say what to look out for after a head injury at all. He was allowed to wonder out in the middle of the night on his own. Appalled as after a concussion they can reoccur and he couldn't have been on his own lost etc, they didn't make sure he was collected . I was in shock at the time and didn't think to go in and ask. I tried to ask someone on the phone why this was and they were extremely rude.