Display Latest Post on a Page Conditionally

Possibly you could wrap the code on the vendor’s page in a comparison. So if the vendor’s name is the Title of their page, and the newest post has a meta field that hold’s the vendor’s name, it could look like this:

$my_most_recent_post = get_posts( 'numberposts=1' );
$my_most_recent_post_id = $my_most_recent_post[0]->ID;
// Get the featured item's meta information here
$meta = get_post_meta($my_most_recent_post_id, 'my_custom_meta', $single = true);

if ( $meta == 'Featured Vendor' )
{
    // display the featured vendor information here
}

I’m assuming that you’re storing vendor information with all your product entries. Whether you store the title of the vendor, the unique ID, or the slug, that comparison should be similar.