It seems to work OK on my iPhone. The Facebook & RSS feed icons in the left sidebar appear at the bottom. And on a mobile device, the post text is supposed to disappear, leaving just a thumbnail of the featured image and the post title. Did you notice some other behavior before?
If you want the thumbnail to span the width of the screen, you can try adding this CSS to your JetPack Custom CSS:
@media screen and (max-width: 400px) {
.list-view .site-content .post-thumbnail img {
width: 100%;
}
}