You guys know what you are talking about, and your conversation is not inherently or purposefully misleading. However I see an opportunity to clarify for other readers -- especially those wanting to provide vegan products -- what true silk is. I hope you don't mind the interruption.
Silk is a natural protein fiber produced by some invertebrate animals. For example, moths produce silk cocoons and spiders produce silk webs. At a certain level, I think most people know that. But it gets confusing when used in context with plants like corn, mulberry, and bamboo. While corn silk, mulberry silk, and bamboo silk are all valid terms and real things, they have some distinct differences.
Corn silk isn't true silk, it's a natural plant fiber. As far as I know it is not used in soaping but I could be wrong (if it can be done, it probably will). Bamboo silk, as clearly stated by Megan and Carolyn, is a man-made fiber originating from bamboo.
Mulberry silk is real silk made by the mulberry silkworm (which I presume feeds on mulberries). And tussah silk, which I had never heard of until soaping, is also made by a silkworm. These silkworms are "farmed," for their cocoons, and usually they are killed when the cocoons are harvested. If left alone, the silkworms would have developed into moths. The moths are not allowed to leave the cocoons because that would cut the fibers and compromise the strength of the silk.
I have no problem with commercial silk production or silkworm farming. I am not trying to alarm anyone or nudge anyone to examine their environmental ethic. I am not vegan, nor do I consider myself inhumane toward animals in any way (to the contrary, animals are my life-long passion -- I am a biologist). I simply share this information because I have never seen silk discussed in depth on this forum in relation to vegan products, which are important to many soapers. Actually, my hat is off to Megan for acknowledging right from the beginning that bamboo silk was likely a vegan alternative to tussah silk.
That is all - thank you!