Sandton City refuse to acknowledge negligence

I went to Sandton City on the 10th of July 2022 for shoping, when I got back to my car I find my DJ equipment ******. Sandton City told me they don't have the footage because I was parked at a blind spot. I went and asked to look at their cctv footage and I could see my bakkie, however there is a footage missing. It will seem like it was deleted. You could see my bakkie from 18h30 ,but the at 20h30 the video jumped. I reported and wanted to clean from their insurance for their negligence and they said they are investigating. It's been 2 month now. I paid for parking so that I can shop at a safe place and I ended up losing 80k worth of belongings. My insurance could not cover the equipment because there is no forced entry and there is no footage which shows breakin.