I recently reinstalled the game and didn't log in to Facebook because I can't log in that way either, and my saved progress on the device is still intact, I didn't know that was possible.
I'm not sure if this happens to everyone, because as I emphasize, I didn't know it was possible, I thought that if you deleted the app, your unsaved progress on Facebook (i.e. saved on the device) would disappear and I would have had to start again, but apparently it didn't happen, but as I said before also, I'm not sure if it can happen to everyone because I wasn't even aware of it jsjs.
sorry for the long text XD