Since my game started saving on the wrong Facebook account, I tried restoring it and I followed this method, provided by D3’s own support staff:
The first option is for you to unlink the data on your end, by following these steps:
- Please Force Close the game.
- Make sure you are logged out of the Facebook app on your device and the native integration on iOS and Android devices under Settings>Facebook.
- On a computer or separate device, log into the Facebook account that you want to clear the backup data from.
- Click on Games>Apps>Marvel>Settings>Remove.
- Launch your game, then log in with the desired Facebook profile.
You should not have an overwrite, but if you do, let us know and we can restore it.
This effectively made all my game progress vanish into thin air, so DON’T ever use this method!!! Ever. 
I don’t even know what happened. One minute I had all my game progress on my phone and the game was running just fine, the next minute when I clicked “save backup to Facebook” and logged in, the game restarted from the beginning again and all my progress was totally gone. All I can do now is to sit here and look sad while my excellent season ranking in the top 10 goes down the drain. Bye-bye to those 2-3 10-packs I would have won eventually… 
The only thing I can do now