if data was synced, you'd just bring back whatever the error was. Unless it was narrowed to only certain data.
Not according to the Genius that helped me with my phone a couple of months ago.
According to him, an iTunes backup is a literal clone of everything down to preference files, caches etc. All the places that get corrupted.
A Sync is literally a fresh file of the data from your computer placed on your iPhone. Like, he put it, a very fast little gerbil is reading the info from your computer's contacts app etc and typing it into your phone for you. All the cached stuff was never synced to the computer so there's nothing for the gerbil to read. Which is why you lose your safari history etc when you do a sync.
I thought his allusion was so funny that I didn't have the heart to tell him that I'm not so stupid I needed that kind of description.
Given that I followed his instructions and did NOT use a backup but did a sync and the problems didn't returned I'd say he had it right. The only thing I lost were a handful of text messages but they really weren't that important.
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Ok, but then iCloud will back up your entire device.
So losing data over a device getting replaced at the Genius Bar is impossible, isn't it?
if you are doing it, no you really can't lose your data. But some folks aren't and then they freak out at it taking 3 hours or having to pay for more storage to fit all 40 GB of stuff that they have on their 64GB iPad and their 32GB iPhone. they don't want to hang out at the store, they pitch a fit that they can't just leave the phone and they pitch a fit that the store wants them to go home, run the back up and then come back. So I can see why Apple might want to find a solution, but I can see a lot of potential legal issues in this particular alleged method that is perhaps unneeded if they would just ramp up the education of customers.