incompetence and no consideration for customers

I was booked on a flight to Victoria falls on the 24th June at 11H25. I arrived way in advance at the airport and was travelling with a 17years old daughter and a friend. She is turning 18 bin December. I realised when they asked for an Unabridged birth certificate that I forgot it at home. I quickly sent for it and when it finally arived it was 11H24. I ran to check in and the lady started checking the documentation and was not sure if the affidavit would suffice. so she stood up to go check with her supervisor.They went through a training document to ascertain that all was well. Later they let us go to board. Needless to say while they are checking our names were being called. When we arrived, the gates were closed and there was no one to open the gates for us even though the flight was delayed for an hour. I waited in anticipation that someone will come open but no one did. Evetually we went back after asking people around where we needed to go as there was no rep from BA Comair, on arrival at ticket sales desk we were told we have forfeited the money used for booking as it was past 30 minutes afiter the flight had left. I tried to explain that it was not my fault but no help!