Patch of hair fell off after highlighting service

I went to Jeauval salon, Northgate, Johannesburg, about 2 weeks ago, 17 Dec 2017, to get my root colour freshened up. The highlights, which were recommended by the 'expert' hairdresser, were left in too long. When the job which cost me a little under R1000 was done, the result was a 'cheap-looking' orange colour which I was not satisfied with. I had been leaving the country that evening (which I had trustingly made them aware of) so i did not have time to get it remedied then. A week later, I went to a clothes store and only then noticed in the mirrors that reflected the back of my head, that a huge patch of my hair was missing. I was horrified as my hair is dark and grows thick and healthy as I've always been careful to get my hair professionally colored and use professional products to maintain it and to prevent exactly this situation. I am really furious right now and feeling self-conscious and depressed. In retrospect, i realized that none of the ladies at the salon had held up a mirror behind me to show me their failed result. It is clear now as to why this was not done. I am really disappointed.