Retrieves post data given a post name, type and parent ID.

functions.php

<?php

/**
 * Retrieves post data given a post name, type and parent ID.
 * 
 * @return WP_Post|NULL
 */
function get_post_by_name( array $args ) {

	global $wpdb;

	$args = array_merge( array(
		'name'		=> '',
		'type'		=> 'post',
		'parent'	=> 0,
		'output'	=> OBJECT,
	), $args );

	if ( ! $args['name'] || ! $args['type'] ) {
		return;
	}

	$args['parent'] = intval( $args['parent'] );

	if ( $args['parent'] < 0 ) {
		return;
	}

	$sql = $wpdb->prepare( "
		SELECT ID
		FROM $wpdb->posts
		WHERE post_name = %s
		AND post_parent = %d
		AND post_type = %s
	", $args['name'], $args['parent'], $args['type'] );

	$id = (int) $wpdb->get_var( $sql );

	if ( ! empty( $id ) ) {
		return get_post( $id, $args['output'] );
	}

}