Why did my iPhone delete all my contacts?

I picked my iPhone 4 up to reply to a text message, and when I tried to open that message my phone froze and wouldn't open my message, phone, Bing or Google apps. I had to turn the phone off in order for the apps to open, and when they did all of my contacts were gone. What could cause this?

A rogue Android.

Cuz it doesnt like you!