Sudden disappearance of contacts on iPhone

Sounds frustrating, especially since you’ve already tried the main iCloud synch steps. If contacts have suddenly disappeared, it’s probably due to a sync source issue rather than deletion. Here are some tips:

Go to Settings > Contacts > Accounts and check if you have multiple accounts (iCloud, Gmail, Outlook, etc.) Sometimes contacts are stored in a different account, and toggling iCloud wont affect those. Turn each account’s “Contacts” toggle off and back on one at a time to refresh.

Login to iCloud.com then press Contacts. If the missing contacts are there, they just aren’t syncing to your iPhone. Trying signing out of iCloud (iPhone Settings, > your name > Sign Out) and back in.

On iCloud.com, click your name at the top then press Data Recovery and select Restore Contacts. You can roll back your entire contacts database to a previous date.

Open the iPhone Contacts app and tap Lists or Groups in the top left. Make sure all groups are checked, some can be hidden because their group isn’t selected.

If none of the above worked, it may be worth contacting Apple Support directly. They can check your iCloud server logs to see if there was a sync error.