lost contacts

Sync them back from whatever application you are using on the computer or cloud service.

What cloud service or contact manager are you syncing them with? do they still appear there?

Got the same problem and solve it next way - I found that my account with synced contacts suddenly was deleted, so I lost all the contact with it. After I sync them with my own mail server everything was great and I still got no problem with it. So just check your account for syncing. Hope it will help you.