I'm sure there have been some hets and some Gravel type animals sold as Normals before but time, effort and patience is the only way to find out. I believe there are still a lot of genes out there that will look normal but can have big effects on other morphs. As far as Normals go, before this explosion of morphs people did line breed some interesting Normals. I have some really old ball python books with pictures of "Gold Banded" ball pythons and darker colored ones with almost Black Pastel looking patterns but it was completely polygenic. Some morphs actually require a bit of polygenic breeding into a certain morph before mixing it with others and creating something else. A video I saw from NERD talks about a specific line bred animal as the one used to create a particular morph 2-4 genes later.