Side note: I talked to an Apple developer at WWDC and was told that HealthKit data never leaves the device (isn't synced with iCloud). Hence the lack of the iPad app. Given that, if the data is lost, its probably gone forever.
Apple backs up your Health data in iCloud, if you enable it.
"Your data in the Health app is encrypted with keys protected by your passcode, and never leaves your device unless you choose to back it up or grant access to a third-party app. When you do choose to back up your Health data through iCloud, it is encrypted both in transit and on our servers."
"...only in encrypted iTunes backups...", I think certain encrypted data is also stored in iCloud backups as you're required to authenticate the restore before it continues. An iCloud restore recently brought back all my email password settings etc, but an iTunes non-encrypted restore lost them.
The problem with HealthKit is the lack of testing. Developers may have had the beta app for months - but it couldn't do anything. The app relies (mostly) on data from third party apps and due to the beta testing limitations (100 devices) people running iOS 8 betas couldn't install HealthKit beta apps and test them with the HealthKit app. Same things applies to keyboards which I've found to be very buggy and I think most of it is on the OS side not the keyboard app side. Hopefully this won't be as big of an issue next year with the new TestFlight service (1000 users limitation).
I've seen this problem and I think what's going on is that the service that's keeping the data is having problems catching up.
I noticed yesterday that the data was missing. But it reappeared later (though the dashboard was missing). When checking the data manually (getting to somewhere that has data, like Walking + Running distance) and trying to get all the data, it seems to try to load data, but doesn't get it (spinning wheel)
Given that the data was available later the same day, I'm guessing that the problem is related to services that are not as available as they should, probably due scale after all the devices using iOS 8.
>> "Given that the data was available later the same day, I'm guessing that the problem is related to services that are not as available as they should, probably due scale after all the devices using iOS 8."
All data is stored on the device, there is no cloud component so this is unlikely.
I've had this happen a few times (iPhone 6, iOS8.0.2), but I've found that powering off my phone and restarting seems to restore the data. None of it is truly gone for me, it remains logged and listed, but it's almost like it cannot access the database of data that's stored and it gets a bit wonky but I'm not certain on that. Hopefully Apple will have it fixed for the next version or the app will be dead in the water.
Yeah I've had to restart my phone four times so far and the data does seem to come back, but anything that was logged during the time it didn't work isn't there.
Also, it seems to be losing whole days' worth of data from the MyFitnessPal app. For example, I'll have today's Nutrition data in there but tomorrow when I add breakfast it will likely have lost all today's data so the graphs always start "today" even though I had put data in yesterday. I'm not sure if this is HealthKit or the app, though, because things I put in manually using the Health app seem to stick.
Re; MyFitnessPal, I've not experienced that but I've only logged 3 days worth of data so far since I connected it to HealthKit. It does seem to be an inconsistent issue for people as well, which makes it harder to determine which part is at fault. I think it's probably HealthKit as MFP reads data in (steps etc) fine.
This is similar to my experience (iPhone 5S, 8.0.2), though often I don't even need to reboot. Open the Health app; no data; close it; do something else for 1-2 minutes; reopen - data is now visible.
I tried the leave it and come back and it didn't work for me, only a full power-off cycle. It does seem to be slightly different quirks across different user devices.
I am curious if it is related to just iPhone6 models or if anyone is noticing it on the older models. I have an iPhone5s and have had no problems so far.
My dashboard only contains a few things I entered manually, and fortunately it's still there. I haven't been using a 3rd party app, yet. (iPhone 6 w/ 8.0.2)
The step data is surprisingly fine grained. I will get 5-10 data points per minute, just walking around the house. So while it seems like a basic thing, it's probably the most data by volume that HealthKit is tracking.
