That's exactly it. Unless someone posts on their own, we generally do not disclose this information. Many people do not want it known publicly they are away, how far away they are and how long they will be gone.
Additionally, although Prime is a great site and wonderful for our community, the NSXCA has no actual affiliation with Prime and many attendees over the years have indicated they do not even frequent Prime (amazing, yet true). As a club where members must pay dues (albeit nominal), we respect the general wishes of our membership to retain and protect their privacy rights.
Indeed, most of the Colorado members/attendees are not on Prime.