From A Day by Day Chronology of Mr. Sherlock Holmes according to Zeisler and Christ compiled and edited by William S Dorn:
On May 23, 1889, the Naval Treaty was stolen. [NAVA]
The chamber into which we were shown was on the same floor as the drawing-room. It was furnished partly as a sitting and partly as a bedroom, with flowers arranged daintily in every nook and corner. A young man, very pale and worn, was lying upon a sofa near the open window, through which came the rich scent of the garden and the balmy summer air. A woman was sitting beside him, and rose as we entered.
“Shall I leave, Percy?” she asked.
He clutched her hand to detain her. “How are you, Watson?” said he, cordially, “I should never have known you under that moustache, and I daresay you would not be prepared to swear to me. This I presume is your celebrated friend, Mr. Sherlock Holmes?”
This is one of the rare instances of a physical description of Watson in the Canon, and the one scholars use as proof that Watson had a moustache.
“A cold hand seemed to close round my heart. Someone, then, was in that room where my precious treaty lay upon the table. I ran frantically up the stairs and along the passage. There was no one in the corridors, Mr. Holmes. There was no one in the room. All was exactly as I left it, save only that the papers committed to my care had been taken from the desk on which they lay. The copy was there and the original was gone.”
Since Phelps was warned strongly about the need to keep the treaty safe, why did he leave it on the table in the first place? Why did he not put the original in his desk drawer and lock it up or lock the room before leaving the floor?