Sorry to hear about your spill, and welcome to the forums.

Were you signalling during your turn? I generally signal before my turn, then put my hand back on the bar before actually turning. I'm usually also braking a bit before hitting a sharp right turn, and since my front brake hand is also my signalling hand (left), it's just a quick signal to show my intentions, then hands on the bars braking and turning.

Also, there could be a dozen reasons why you spilled - loose grit on the road, an irregularity in the pavement, could have just been a fluke.