Recovering lost contacts in WhatsApp
If you’ve given WhatsApp permission to access your device’s address book, WhatsApp will add any contacts with an account to your WhatsApp contacts list.
You can only restore lost contacts if you’ve previously made a copy of them using your phone’s features.
WhatsApp can’t restore your contacts for you.
Note: If you unblock a contact or phone number which wasn’t previously saved in your device’s address book, you won’t be able to restore it to your device.