I f ALL your plants came with this stuff, I'd vote for live long-fiber sphagnum moss. It is often used as the substrate or packing material to send live plants because of its moisture content. Or perhaps it is another type of moss. If you are getting some kind of CP with your other plants, I'd say...lucky you! (I did get a "gift with purchase" last summer...bought a pot of s. psittacina and found a sundew in the pot!...I was thrilled.)

A pic would be good if possible.