get_page_by_title() doesn’t return the post object if the title has inverted comma (‘)

Take 2 on my answer:

get_the_title uses the the_title filter, which turns your apostrophe into a right single quotation mark. When you then plug the resulting string into get_page_by_title, you don’t get a match – because ’ is not the same as '.

So, bypass the_title filter completely:

$post = get_post( $extraPostID );
$extraContent = get_page_by_title( $post->post_title, OBJECT, 'post' );