You can Pick up Items and it shows the animation without any Inventory Space, Making the item Disappear.

How to Reproduce:

1: Fill your Survival inventory

2: Go in the Creative Inventory and grab a item of choice

3: Drag the Item out of the Inventory so it Drops

4: Press "E" to Exit the Inventory

5: Walk to the Item Like you are going to pick it up

6: It looks like you picked it up but if you check your Inventory it Disappeared!