I've had my iPhone 4s since December of 2011 and never had any issues with it. Last Monday, I was out with my friends and wanted to send a picture to one of them and realised that all my messages no longer had contact names. I then went into "contacts" and saw that absolutely every single contact was gone/deleted. I had done nothing. Half an hour beforehand they were all there.
They all just disappeared on their own. Does anyone know why this has happened? I do not sync my phone to a computer or iCloud because I have an extremely old laptop which tends to play up with anything related to Apple. I lost a bunch of phone numbers forever (not that it matters, I never keep in touch with those people anyway) but I just wanted to know why this happened. Is it a virus or what? Other people have said they experienced the same thing. Nobody knows why though.