Floating Social, Pinterest, Featured images, Thesis theme

I think the Thesis theme does featured images weirdly. The Pinterest option doesn't show even it I use their "Post Image" option... The normal 'featured image' box is absent. If forced by customizing functions.php (actually, in Thesis, this is custom_functions.php) Floating Social ignores the featured image... though the image has a ".post_image" class... any ideas on how to make this work?