After accidently trying to throw the item [Green Key] on the ground, I noticed that this was not possible. But I did believe that there was a way to get it on the ground, it didn't take me long until I tried to put it in a chest (which worked perfectly fine), and then break the chest. To my surprise, I managed to get the key on the floor. Honestly, I am not sure if this is a bug or not - but I do believe that this should be dealt with, just incase someone accidently breaks their chest without knowing that it might contain keys in it. Anyways, here is a video of the bug. Solution: Make a chest unbreakable if they contain a key.