There are two ways for you to restore iPhone data: directly scan your phone and extract your iTunes backup. These two ways let you restore contacts, SMS, photos and more. Read more: http://goo.gl/PvUo6e.
You could possibly retrieve you lost data by simply syncing your phone with your computer by plugging it in via USB port. Hopefully you at least used your computer once with the phone which stores and saves info. As to what could have caused it, not to sure. Only contacts and calendar events? Or were apps affected to?
3 months ago
Last edited at 1:42AM on 12/15/2013
If you want to recover the lost data, follow the below way.
If you have already backed up your iPhone with iTunes, you can recover deleted data by the following steps using iTunes: Click the File menu and select Devices > Restore from Back up. Or Open the iOS device's Summary tab. There are two ways to access this: Click the device button in the upper right corner. (If viewing the iTunes Store, click the Library button in the upper right corner. The device button will then be visible.) From any view in iTunes, click the View menu and select Show Sidebar. Select your iOS device in iTunes under Devices. Click the Restore Backup button.
If haven't had time to back up your iPhone before the deletion, there are also two methods for you to retrieve lost data of iPhone: 1. Recover the lost data directly using a third party software; 2. Recover the lost data under DFU mode. Read more: http://goo.gl/OSjc4X.