How to restore lost contacts/address book?
If you use Time Machine, just open the Contacts app, and THEN go to Time Machine (Click on the menubar icon / Enter Time Machine)



Once there, you can "travel in time" to an older date and find the missing contact. This is where you select the contact and click "Restore".




You don't need to restore a folder or file, but the contact (in the Contacts app) itself.