(Seen in both Creative and Survival on an iPod Touch 4th Generation and a Kindle Fire HD 7)
When tapping an item in your inventory (as it is being placed into your hotbar) a white flash is placed over the first hotbar slot, although it is shifted a pixel to the left of what it should be (It protrudes into the frame by 1 pixel to the left and only reaches 1 pixel away from the box's right edge).
Not confirmed in iPod Touch 5g