iphone has lost contacts

Contact sync to iCloud is only for contacts associated with your iCloud email address. Contacts associated with, say, gmail contacts will be visible in Google contacts. Similarly, for outlook contacts, yahoo, AOL, etc.

Hello there James_Apple_,

Welcome to Apple Support Communities. So we can confirm, do you have a current backup of your iPhone data in iCloud? If so, follow the steps from the Apple Support article to restore from that backup: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Restore your device from an iCloud backup

1.Turn on your device. You should see a Hello screen. If you already set up your device, you need to erase all of its content before you can use these steps to restore from your backup.

2.Follow the onscreen setup steps until you reach the Apps & Data screen, then tap Restore from iCloud Backup. 

3.Sign in to iCloud with your Apple ID.

4.Choose a backup. Look at the date and size of each and pick the most relevant. After you choose a backup, the transfer starts. If a message says that a newer version of software is required, follow the onscreen steps to update. If you don't see onscreen steps to help you update, learn what to do.

5.When asked, sign in with your Apple ID to restore your apps and purchases. If you've purchased iTunes or App Store content using multiple Apple IDs, you'll be asked to sign in to each. If you can't remember your password, you can tap Skip this Step and sign in later. You won't be able to use the apps until you sign in with your Apple ID.

6.Stay connected to Wi-Fi and wait for a progress bar to appear and complete. Depending on the size of the backup and the network speed, the progress bar might need a few minutes to an hour to complete. If you disconnect from Wi-Fi too soon, the progress will pause until you reconnect.

7.Now you can finish setup and enjoy your device. Content like your apps, photos, music, and other information will continue to restore in the background for the next several hours or days, depending on the amount of information there is. Try to connect often to Wi-Fi and power to let the process complete.

If this does not restore your contact, reach out to Apple Support for further assistance:

Apple Support

We hope this helps you.

iPhones do not manage contacts, they just display contacts associated with one or more email accounts. So if you delete an email account you will lose the contacts that it hosts. Likewise if the email account is not accessible, either temporarily or permanently. If your only email account is your iCloud account then this will help→iCloud: Restore contacts, calendars, and more in iCloud Settings. If the contacts are associated with any other email account you will have to see what recovery options the ISP that hosts the accounts has.