Featured Image disapeared from 3.5

I use a theme (leet press) that uses the featured image meta-box to add the image that will be displayed on the main page AND in another section it uses it to add the image to the main slider on the main page. After updating to 3.5, this feature disapeared as the meta-box don’t even appear in the screen options toggle menu to be added. Does anyone have any idea to get it fixed or add it back? Thanks