Contacts In Address Book

 For future reference, the next time you need to delete only from a group, click on the box to the left of the contact in the list to select it, and then in the toolbar click on the "hamburger" icon to the right of "Delete", and you will see the option to remove it from the group.  Using that menu does not remove the contact from the address book----only from the group.  It looks like this--------------------------

As for recovering the ones you deleted, click on "Collected addresses" in the left pane.  Unless you have the feature turned off, any addresses you have sent to or gotten emails from should be in that folder.  Bit of a long shot but worth a look.  If you find them you can then drag and drop them back into the address book.  Or, for multiple ones you can also check the box for each one, then click on the hamburger icon in the toolbar and either Move or Copy them to the address book.