Firstly,we should make sure the contacts are really gone..
Try to hold the search option on the contacts,if there is anything in the field,it will affect where the contacts are belongs to...
Then check the red ribbon on the right named group,tap it and see whether you can the right address book or not and/or select the group...The ribbon will not be there depends on how you set up your contacts.
Thirdly,try to press and hold down the power button,when the shut off image appears, and then restart the ipad,waiting for the appear of apple logo.
If your contacts are still in limbo, there is one other possibility.
If you have not synced your iPad to iTunes since the contacts disappeared, they may still be in your last backup.
Open iTunes (without the iPad connected) go to Preferences, and the Devices tab. You’ll see a list of backups, only one per device that you sync with iTunes. Check the dates.
While you are there, turn off auto-sync. It will make it easier to manage when you iPad syncs in the future. It’s important now, because you don’t want the iPad to start syncing when you plug it in. The first thing it would do is overwrite your backup.
If that looks good you can choose to restore your iPad data. You will lose everything stored in a app since the last time you backed up the iPad. So go through all your apps first and save the important files, photos, whatever to the computer, or email them to yourself.
Connect your iPad.
In iTunes, under the Device list, right click on your iPad and choose Restore from Backup. Be sure it says ‘from Backup’, not just Restore. Select the backup from the list and cross your fingers.
Hopefully that worked. If not, and you don’t have your contacts backed up in some other program, you are stuck with entering them again manually.
In the future I recommend syncing your Contacts with an online service like Google. It will be a lot easier to recover them if anything happens to your iPad.
Hope it will work then,..