Contact disappearing

I have this really strange issue that started yesterday. It seems that certain contacts r getting deleted...For example my daughter. I can see her messages to me in "messages" however her name is gone and the only thing there is her number. Now when I go into contacts her info is gone completelly.. Now there is another contact I have that it is happening to it also. I have gone in and readded them and its ok for a few mins and then it disappear again.. I have backed up my phone and have even restored it, with no luck.. Any ideas whats is going on.. I have the 4s and I have had it for awhile without any issues except for now.. Thxs for any help...