I logged on today and did all my dailies, arenas etc. Logged back on a few hours later, and none of that was saved. I’m not sure the exact time frame that got reset.
Made no difference to me. It was a total reset (including stats/upgrades etc) so I just redid the day.
I think a very minor version of this happened to me once, when switching between devices (iPhone and iPad). I wasn’t 100% sure though, so I didn’t report it.
If it did happen, might have been because I had not completely closed the game on either device, so when I switched I don’t think the game knew to reload the data. Maybe.
I now do things differently. Each time I quit playing, I always:
Manually save the game.
Close the app completely.
If there is/was a problem, I never experienced it again. And I have been looking. But like I say, can’t prove it actually happened even the one time. I just think it did.