I wouldn't be surprised if Apple has their own internal iCloud network. Just like Google has their Apps for Business, Apple could have one but just inwards-facing and not hosting any other business.
This means even if you have his internal FaceTime/iMessage ID, you wouldn't be able to contact him because his account and yours exist in 2 realms.
Then again I guess he'd need an external-facing one for public VVIP to FaceTime him. Maybe he just carries 2 phones?