The trigger price of my stop loss order was never hit as per the charts and yet my SL got triggered, why?
All trading and charting platforms will display only 1 tick (buy/sell transaction on the exchange) per second on a chart, whereas there could actually have been hundreds of ticks (buy/sell transaction on the exchange) in that 1 second.
Since you are seeing only 1 tick on the chart, it is quite possible that you don't see your Stop Loss or limit price that got executed on the chart (be it on NSE, yahoo, NEST, or anywhere else).
To learn more, read this post on TradingQ&A.
You can verify the trades executed on the exchange. Read this article to know more