Okay, let me see if I can break this down:
* A card that has a when-gain effect with a different gain destination does not visit. (Nomad Camp)
* A card that gains another card and puts it somewhere else does not make that card visit. (Transmogrify, Explorer, Mine, Armory)
* A card that does something when something else is gained does so after that card is gained, and the gained card does visit, and can be lost track of. (Watchtower, Royal Seal)
Just to check, if I gain a Nomad Camp from a person I'm Possessing (a would gain effect), that NC goes on the top of my deck, right?
Man, lots of italics.