There are many way a document can be lost: it can be lost in flames, flooded or even blown away and buried, as all the four elements (fire, water, air, earth) can get ways to do what they like, but although not always, we can somehow deal with them. However, for the notorious fifth element, ether, we are not as lucky. The document lost is not retrievable. For burnt pieces, as long as the ashes are staying at their places, we could use a special machine to restore the information; for the dampened papers, we can put them into a refrigerator and pray till the dampness and vapour are gone; for those gliding we can fly a balloon and get them; and for those concealed with mud we can simply use a spade and remove the quagmire; but to my regrets, the document lost in the fifth way being retrieved is the last thing possible on earth, mind you, and never do you try and get them; there are no points doing such a fool's errand.