This is very curious, I assume that if you've had a hot and cold stone massage qualification, a lot of these cover stone use for facials (even if these weren't practised you may have covered the theory).
If you have done a hot/cold stone in your massage training, it would be good to refer back to your course curriculum to see if this was indeed covered so you can provide this to your insurer when you pose this question.
I say this as I had a similar question regarding infrared light/heat lamp for massage therapy, which was indeed covered on my course. It was touched on so briefly that I had completely forgotten that this was the case and ALMOST signed on to a specific course.
Thankfully, I found in the curriculum where this was covered and it satisfied my insurer.
Regarding specific training with Gua Sha, I have not researched this and am not aware of any formal training in this technique.
The safety profile is high as these are simply cool stones and if you have facial qualifications, the same general contraindications would apply.
So, double check what your training covered (even if it's not gua sha specific but covers cool stone massage) and of course talk to your insurer : )
