Shadows in the stars, we will not return!
Nicko probably didn't go to NAMM because he's still recovering from fracturing his wrist, plus neither Paiste or Sonor were releasing/displaying anything new having to do with him or Maiden.That plus I’m not sure why Maiden working on an album is something that needs to be kept secret. They’ve made hints about it before. Even last year Steve alluded to something in an interview.
I don’t think the band is being intentionally secretive. It is more that if they are working on an album, there’s nothing to blab about at this stage. I wouldn’t read Nicko’s absence as a sign that there’s something under wraps.