I just had this issues twice in the last week. I am hoping for a bug fix soon?!?
This first time, when the error message came up and it gave the options to retry, cancel, or continue without saving, I selected retry a few times and the continue without saving. I restarted the game and system and everything was gone, so I tried to delete the save from the console and reload from the cloud and everything was still gone.
Last time this happened, when the error message came up and it gave the options to retry, cancel, or continue without saving, I selected cancel. I then immediately quit the game, and turned off my xbox. After a few seconds I turned everything back on and loaded up the game. I lost the last few minutes of the save, but everything else was there and it is still working a couple days later.
I am not sure if I just got lucky the second time or if this is a work around. Maybe this is just something to try if it happens to anyone else, until it gets fixed.