Restore OS X Keychain

The Library folder where your keychains are stored is hidden by default.

First, quit Keychain Access.app.

Open Finder and press Shift Cmd G, then enter ~/Library/Keychains. Here, rename the existing default file, and drag your original file back from the Trash.

Restart Keychain Access and you should see your old one restored.

It's very simple to restore a keychain with macOS Mojave (and maybe earlier versions too):

• copy the file ending with keychain-db extension, most commonly login.keychain-db, to ~/Library/Keychains with a different name to avoid overwriting the current version
• launch Keychain Access
• on the top menu, click File, then Add keychain, or Shift-Command-A, then point the dialog to the recovered file

You can view items and unlock the keychain with the keychain's password. The first step of copying to that location is because Keychain Access does not import the keychain, so if you delete the file, you also lose the keychain.

Here's a way to restore passwords lost back into the Keychain content.

Keychain Access will lose saved passwords often when there's a stored password in Keychain desired to be deleted; and once the item is highlighted and Edit > Delete is clicked, and, instead of just clicking the 'delete file' button, the 'delete file and all references' button gets clicked.

1. Open Keychain Access (located in the 'Utilities' folder)
2. Go to the "Keychain Access" menu > select "Preferences"
3. Click the "First Aid" tab
4. Make sure the "Synchronize login keychain password" box is checked.
5. Close the Preferences window.
6. Go to the "Keychain Access" menu and select "Keychain First Aid"
7. Enter the administrator's username & password
8. Click the "Repair" button.
9. Click the 'Verify' button.

Now go ahead and restore all the missing, previously saved passwords back into Keychain Access:
1.) Quit the Keychain Access app.
2.) Goto ~/Library/Keychain/login.keychain file, then highlight it
3.) Enter Time Machine
4.) Goto a previous date's restore-point wherein Keychain Access held all your passwords correctly
5.) Click on 'Restore this file' —> replace the unwanted current version of this file;
6.) Goto ~/Library/Preferences/com.apple.keychainaccess.plist file, then highlight it
7.) Once again, enter Time Machine
8.) Select that very same previous restore-point-date that was used to restore the login.keychain file
9.) Click on 'Restore this file' —> replace the unwanted current version of this file.

Reopen the Keychain Access app and assure that all inadvertently deleted passwords were indeed restored,
and then
Go to the "Keychain Access" menu and select "Keychain First Aid"
Enter the account's username & password
Click the "Repair" button.

Close the Keychain Access app.