WordPress query single post by slug
From the WordPress Codex:
<?php$the_slug = 'my_slug';$args = array( 'name' => $the_slug, 'post_type' => 'post', 'post_status' => 'publish', 'numberposts' => 1);$my_posts = get_posts($args);if( $my_posts ) : echo 'ID on the first post found ' . $my_posts[0]->ID;endif;?>