I gotta explain something about
Brassavola nodosa. In the wild, this orchid is very, very adaptive. It has been known to be an epiphyte growing on trees, and it has been recorded to be a lithophyte growing on rocks. This is why you are getting a lot of varied answers. If you understand this, then this will all make tons of sense.
These are some pics I found on the web showing it growing as an epiphyte:
https://farm8.staticflickr.com/7346/...224942606e.jpg
https://c2.staticflickr.com/6/5509/9...a916f006_h.jpg
Here's a pic of one growing on rocks:
http://fireflyforest.net/images/fire...a-nodosa-1.jpg
If you want to read a blog:
Lady of the Night Orchid (Brassavola nodosa) - The Firefly Forest