If an earlier version of your sitemap contains a page with a Thing assigned to it (e.g. mybubbleapp.com/product/great-widget-1), and later that Thing is deleted, Google may still list that page online even after you upload an updated sitemap. This is because regardless of what your most recent sitemap says, Google will try to visit old URLs to see if they're still alive. Since a Bubble page will still technically load even if the assigned Thing doesn't exist (it just doesn't show any Thing's data), Google will think that old URL is still alive.