"Signage for access in late evening"

I had to drive across London to collect my daughter after day surgery. I was told to come at 9pm and on enquiry was assured there would be no problem getting in at that time. Unfortunately, I was delayed by very heavy traffic and arrived at 9.30pm, after driving for an hour and a half, to find the main doors locked. The one remaining person on the desk inside stood with their back to the doors and steadfastly ignored myself and three other people outside trying to gain admission also for the day surgery unit There are no signs to tell you what to do. After about five minutes we were lucky enough to be passed by an ambulance driver who was able to advise us. Surely it would be a simple enough matter to provide a sign advising people what to do after the main doors are closed. Security cannot be the reason because there was no-one in sight to restrict entry via A&E.