Hi Bo,
You have the "App Server" sync turned on. I don't know why your statistics would have all disappeared. Did anything out of the ordinary happen that you did or noticed before your statistics were deleted? Just one day you woke up all statistics were gone? (This sounds very disturbing.)
I don't have a way to restore from an older time period from App Server.
If you originally had say 100 cards saved of App Server with statistics, they still should be there, unless the app somehow thought that cards that were missing statistics were the "new" version and all sent to server for storage.
Do you have a second device? You can try to turn on sync, go to Decks to Sync, "Cloud Only" section, and download of your decks. Do you get statistics data back?
You mentioned OneDrive backup, but I'm not sure why, unless you were just making a comment that with OneDrive you could have a old backup that you could potentially restore from.
If you want, you can email me at
et@orangeorapple.com and give me your account email address and I can look to see what I have on my server for you.