Every iOS update is an adventure. After upgrading your iPhone to a new iOS version, it could be an amazing experience of new intelligent features; also, it could be a disaster of data loss. For example, your iPhone contacts could be gone after the iOS update. To deal with the situation, here is how to get missing contacts back after an iOS update.
Therefore, to get back your lost contacts, some solution are as follows.
First solution: Recover from itunes backup.
Second solution: Restore from icloud backup.
If you have backed up your iPhone with iTunes or iCloud, you can always get the contacts back by extracting the backup files. But there is a drawback: the current data in your iPhone will be all replaced by the backup files. That means a new data loss.
Therefore, to get back your lost contacts,the fastest and easiest way is using fonedong iphone data recovery
More info you can read: Easily Recover Lost Contacts after the Latest iOS Update