this happens to me all the time in the showdown.
For example, round 2, I am 1.4 yard from an ace. I get the spinning wheel, because obviously the other player has quit out of the app. about 4 minutes pass, and I get a popup saying "Saved Game No Longer Exists".
I go back in and sure enough, I went 1.4' from a bird, to 3 bogeys.
EVERY showdown this occurs.
This has never happened to me and I've played in just about every showdown and except for two times when i was with family and couldn't play the last round, i played all 3 rounds.
If the player closes out their game and doesn't actually hit forfeit about 45-60 seconds will go by then the game should reset back to the loading page and they will have 45 seconds to return. (which they almost never do). This happened to me maybe 4-5 times this last showdown. And every time I was able to finish playing solo.
what to do if it takes longer than about a minute to realize that the other person is gone. or what happened isn't that the other person quit... maybe you are the one that has a poor connection:
The safest way to handle this if it happens, which is rare, is to load up the game on a second device. This will kick you off the first device. And it will be a smooth transition into the game. Finish out the round then go back to your preferred device for the other matches. Maybe once every 4 showdowns i might have to do this. Maybe not even that much.
So if you're getting saved game doesn't exist every showdown my logic is that your connection is probably part of the problem.