Another thing occurs to me, & may or may not be the case: for whatever reason, scents (even like perfumes) don't register (smell) the same to all of us; it might even be that you have a sinus issue (again, pure speculation) that affects how you perceive the scent of Forest Floor? Just a thought anyway...it seems odd that you didn't notice the smell when you first put it in his cage? Personally, I like what I'd describe as the "earthy" or "grassy" smell of moss & such products used for our snakes, but possibly it smells different to you?
Since you observed your snake avoiding the substrate & since this smelled like kerosene or paint thinner*, it's for the best that you didn't ignore this. You don't have to read much news today before you find all sorts of products that have been recalled for contamination, & you have to figure that not all products with contamination get called out-especially if only one or two bags are affected. *Both of those products are highly flammable too- personally I'd probably test that out cautiously in a safe area with a tiny amount of the stuff.