I updated iOS 7 and my contacts were ok then they suddenly disappeared a few weeks after updating. I have no idea if it has anything to do with iOS 7 but when I email someone the contacts are there. When I open the app they are gone. What happened?

I updated iOS 7 and my contacts were ok then they suddenly disappeared a few weeks after updating. I have no idea if it has anything to do with iOS 7 but when I email someone the contacts are there. When I open the app they are gone. What happened?
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Try:
- Reset the iOS device. Nothing will be lost
Reset iOS device: Hold down the On/Off button and the Home button at the same time for at
least ten seconds, until the Apple logo appears.
- Reset all settings      
Go to Settings > General > Reset and tap Reset All Settings.
All your preferences and settings are reset. Information (such as contacts and calendars) and media (such as songs and videos) aren’t affected.
- Restore from backup. See:                                 
iOS: How to back up                                                                
- Restore to factory settings/new iOS device.             
If still problem, make an appointment at the Genius Bar of an Apple store since it appears you have a hardware problem.
Apple Retail Store - Genius Bar