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.