Lost contacts over night

When you say auto sync are referring to a sync with iTunes? Or iCloud? The two are different. And if you are sycning to iTunes and iCloud this could be causing an issue. If you're using iCloud I would switch off syncing to iTunes.

This is not an icloud issue.. I have never used my icloud and my contacts deleted on their own today. I went in to get a contact and my contact page blinked so I shut off my phone and rebooted... Waited then went back into contac list and all my contacts were deleted.. went into my in and going out call page and phone numbers were there, but no contact names.. Since I had never used my icloud on my iphone 4 I decided to turn it on...guess what happened? My iPad contacts went into my iPhone contact list and YES...my iPhone contacts have not returned...My IPad only had 9 contacts on it and yes I did have icloud on the iPad because my husband uses it for theraputic use and those are his contacts... What happened to my iPhone 4 contacts? Why did it happen? I see that it has also happened to the iPhone 5 people contacts...Oh my, how distressful and dissapointing this whole situation is to me. I have doctors for my husband and loads of other contacts that I can not retrieve from anywhere...What happened to no worry apple products? I'm worried as can be....

It sounds like you have multiple devices on the same iTunes store account syncing to the same iTunes, and further, that you have not set up your phone to sync contacts with an address book app on your computer OR with iCloud. If you have multiple devices see: http://support.apple.com/kb/HT1495

For more information on syncing see the manual:

iPhone User Guide (For iOS 6.1 Software)

Yes, but if I wasn't using any back up application and that's a problem for me now, because I can't get my contact list back from a back up... The situation is that... contact deletion is from the apple product..why is that happening apple? We can't blame it on icloud that icloud deleted my contact account...because I wasn't using it to back me up... this happened on it's own through apple service... I have both accounts iphone and ipad under the same account, but only backed up ipad. The back up is not the problem...the loss of contact is the problem and yes..had I backed up my iphone I could retrieve my contacts, I'm not discussing back up... I'm requesting an answer for the loss of my contacts on my iphone4... and further more I don't want everything that''s on my ipad on my iphone....nor my iphone stuff on the ipad...that's why they are both two different devises to use as one sees fit for each devise use...

If you don't want the same content on both devices see the link I already posted. There are several ways to keep content separate. I can't answer why you lost contacts, but you should be able to get them back by restoring them from your most recent backup. And if you don't have one either on your computer or iCloud then you are out of luck. I've had iPhones since the day the first one came out and I have never lost any contacts (I have about 1500), so I can't even guess as to why you lost yours.

Thanks..but I also have had an iPhone since the first one came out and have never had a problem either...including having apple computers..unfortunately my worse apple nightmare has come to visit... I just found out that I'm not the only one that is having this problem of losing contacts...apple is getting many complaints of contact loss in the past two days...so I think again it's an apple problem that no one can explain reson for...Glad you are not in this situation...Thanks for your input....

Wish that would have been my issue... I didn't upgrade to iOS6 because I knew people were already having issues with iOS6....so, the loss of my contacts seems to be an unexplainable event... How annoying and dissapointing this is...

The same thing happened to me, on Feb 4, 2013. Lost all my contacts. I also had never backed up on iCloud or iTunes, so the backup process cannot be the problem. I have an iPhone 4, running iOS5.1.1. I have not upgraded to iOS 6 nor have I ever attempted to. I have heard of MANY people experiencing this same problem on exactly the same day. This seems way to coincidental. Does Apple push updates to iPhone without our knowledge? That would explain the sudden simultaneous loss of contacts, maybe. Or a time/date driven virus?

I had this problem and solved it by going to settings>Mail, contacts, Calanders. Then under accounts, I have iCloud and Yahoo!. I went into icloud and turned on Contacts (smone how it turned off???). then slowly over a few minutes those phantom numbers in recent calls and on favorites began to fill back in. My stuff is a mess because i have yahoo contacts and now icloud contacts. One day i will get my stuff all in one place, but when i have tried to geet it together it says confirm delete contacts. So i cancel. Not trying to loose 700+ contacts