All my contacts vanished (I was not synching or updating)
Last night, my Iphone 4S (iOS 5.1.1) was crashing while running apps, so I turned it off and then back on. The next text message I received just showed the phone number (not my friend's name). I looked in Contacts, but all my contacts were gone. I tried turning it off and on again, but it didn't help. Still no contacts. I don't synch to iCloud. I used to synch to Gmail, but not any more. Now in iTunes, all the Contact synch options are deselected. So I restored from my last back (from a couple weeks ago). Besides losing notes, text messages (also from 3rd party apps), photos (which they don't warn you about at all), and settings, I did get back all my contacts (at least the ones up until the backup was made). I don't know why the contacts disappeared, but other that losing some stuff and the hassle of restoring, things were back to normal.
A few hours later, though, the same thing happened. My iphone was acting funny, crashing while running apps. I tried to look at Contacts, but it also crashed. My guess is that it was busy deleting all my contacts and that's what was causing my other apps to crash too. I turned it off and back on. After that, the apps worked again and I could open the Contacts app. However, as you might guess, all the contacts had vanished again.
I tried minore fixes mentioned in this forum and on the internet, but most are applicable to older phones, synching or upgrading issues, or iCloud.
I am not synching contacts to ICloud or my computer. I was not synching when it happened. I was not upgrading software. My phone seems to be fine on minute and then next, the contacts just disappear out of the blue. Nothing else seems to be disappearing. Just the contacts...
I don't mind restoring from backup every now and then, but I don't want to do it every day.
iPhone 4S, iOS 5.1.1