Yes. It is mentioned in the book "red Harvest", which I just read, which takes place between the books "Deceived" (which has the fall of Coruscant in it) and "Fatal Alliance" another book taking place during this time. So, as much as we used to think they were not discovered until RotJ, that has changed. They are within canon to have one (although, since they are a primitive race, technologically speaking, I'm not sure how he/she got off of the moon of endor).