I think shisha, as you have found out, is a bad idea for making a hot VG essence. I am surprised it ignited, but in general, shisha is actually full of chemicals that are not good. I think you are better off trying to duplicate the flavor with regular flavorings, although that can take a while. You might try soaking it in some VG or PG for a week or so and see (no heat), but again, as much as I like a hookah every once in a while, shisha is not good for you. Contains terpenoids and other aromatics that are not good to inhale.