Check the Contacts app and use the search bar to look for the contact
Open Phone, tap Recents, and check if the number is still in call history
Open Messages and search the person’s name or number
Open Mail and search for past emails from the contact
Check iCloud Contacts at iCloud.com if Contacts sync is enabled
Sign in to the same Apple ID on another Apple device and check Contacts there
Restore contacts from an iCloud backup if one exists
Restore contacts from a computer backup made with Finder or iTunes
Check Google Contacts if your iPhone was syncing with a Google account
Check Outlook or other synced accounts for saved contacts
Look in the Recently Deleted section of your contacts service if available
Ask the person to message or call you so their number appears again
Check shared groups or family devices that may still have the contact saved