WordPress at a glance
function is not described

get_blog_post() WP 3.0.0

Get a blog post from any site on the network.

No Hooks.

Return

WP_Post/null. WP_Post on success or null on failure

Usage

get_blog_post( $blog_id, $post_id );
$blog_id(int) (required)
ID of the blog.
$post_id(int) (required)
ID of the post you're looking for.

Code of get blog post: wp-includes/ms-functions.php VER 5.0.3

<?php
function get_blog_post( $blog_id, $post_id ) {
	switch_to_blog( $blog_id );
	$post = get_post( $post_id );
	restore_current_blog();

	return $post;
}