Actually that had to be removed to support swipe events on touch devices.

If you want to restore it you can, but then swipe gestures will not work. Here is what you do:

1. Go to the file photonic/include/scripts/photonic.js
2. Look for this:
   $('.pp_hoverContainer').remove();
3. Comment out that line – you will be able to see the hover behavior with that, I believe.