Starting with a full inventory in Survival. Try to pick up a new item. You shouldn't be able to pick it up because there's no space in the inventory; however, the item is "picked up" and disappears.

For example, all of my slots were full of other stuff and I killed some blazes. The blaze rods are picked up but because there wasn't a slot for them to go into they disappear. In prior versions they would sit on the ground until there was space in the inventory or until they timed-out.

I tried to duplicate this behavior in a new world and was unable to do so . I'll try again tonight and see what I can find.