I managed to hose my contacts on my iPhone, and my amateur troubleshooting just made things worse. The end result is no contacts on my Mac or iDevices or in my iCloud account. I thought I could easily fix this by restore the Address Book folder (within ~/Library/Application Support from a Time Machine backup, but this doesn't seem to work. What happens is that after restoring the Address Book folder, when I open Contacts, the screen briefly flashes the (correct) contacts, and then all the contacts disappear. Thinking that this is because I was connect to iCloud, I disconnected from iCloud by signing out from iCloud from within System Preferences. Alas, the same problem occurred...a brief flash of the correct contacts followed by all contacts disappearing. Obviously the Address Book folder backup does have a copy of all my contacts. How do restore this and then resync these to my iCloud account?