I don't think you'd see it on the ingredients list. It would be used in the factory for some of the raw ingredients, and wouldn't be on the ingredients list because the intention is that none ends up in the final product.
Just like you don't see "grass" on the ingredients list of yogurt...
It is on the ingredient list when present. I’ve seen it on many body soaps and shampoos. It could be listed as DEA, or as one of the many other items listed in an earlier comment in this chain
That's how ingredients work, since they should not be in there they are not on the ingredient list ... and there should be random testing to make sure there is no contamination (if you live in a country which has actual laws regarding pollutants and contaminants).
Just like you don't see "grass" on the ingredients list of yogurt...