GTA V got uninstalled when I cancelled an update on my XB1s

Try to deselect both automatic updates for the Xbox console and background downloads. That way you can pick and choose what gets updated and when so that doesn't accidentally happen again. When those are on it automatically pushes update, which can not be
very good in areas with subpar internet.

It also be good not to cancel an update all together if its for a game, specifically. Often time a game update is not a separate entity from the game, meaning that if you cancel a game updating... it will delete the game because it can't tack on the needed
update. A game update is kind of like downloading a part of the game, if you don't get it you can't play the game.

This could help.

https://support.xbox.com/en-US/xbox-one/console/system-update-overview

Unfortunately the system is currently set up to delete the entire game if an update is cancelled. The only way to avoid that is to have the update download with any interruptions. I'm not sure why it's that way or if/when it will be fixed.

Next time just pause the update installation when you need your full network speed; if you cancel it, that triggers the automatic delete for the whole game.

You can't cancel updates as it'll cause the whole game to uninstall. I've had it happen to me a few times, once with GTA V and that game is HUGE.

You have to redownload the entire game, sadly.

When you reinstalled GTA V did the amount remaining just stay the same as when you uninstalled it.

What exactly is remaining after GTA V was removed.