Game of Thrones may have given Arya Stark her direwolf moment in Season 7, but Nymeria's only living brother has been MIA on the HBO series for most of the season. Never fear, Ghost is not dead on Game of Thrones. Unless someone is keeping information from Jon Snow in a major way, the big white dog is safe in Winterfell, out of the action.
According to producer Bryan Cogman's Twitter account, Ghost was meant to appear in Season 7 in a premiere episode scene with Jon that got cut. That's enough evidence that he is still alive and well. Granted, Cogman has since deleted his account, but that doesn't necessarily mean anything about Ghost in particular. In the episode "Eastwatch," the direwolf got a little shoutout. Sansa said that she warned the King in the North that "he couldn't leave the North and expect it to just sit and wait for him like Ghost."
Frankly, it's a good thing that Ghost didn't go on the Dragonstone trip or the wight expedition. He definitely would not have survived the undead bears, icy waters, or the sudden appearance of two dragons. Let the direwolf do what Jon and Daenerys can't seem to manage and sit this one out. He deserves a breather.
The most likely answer to why Ghost has been ghosting, even though it's neither very magical nor romantic, is that the special effects budget was put towards more White Walkers, Wights, and dragons than usual this season — not to mention the ice dragon. It's brutally honest, but likely true. Season 7 has been a remarkable change in pace and focus compared to previous seasons. It's not too surprising that some canine characters made the cutting room floor.
Hopefully Ghost will appear in the Season 7 finale if only to remind fans that he's still a factor. The episode is titled "The Dragon and the Wolf," so that's promising. Bran still can probably (and should) warg into him if necessary for protection.
Ghost's absence does sort of indicate that Jon Snow is more vulnerable than usual. The last time he and Ghost were separated, Jon met and fell in love with Ygritte. This seems to be happening all over again with Daenerys. Speaking of the Mother of Dragons, it would be nice to see how she reacts to a direwolf. That may be a lot to ask of the final episode of the season, but Ghost has to return at some point. Might as well make it interesting.