On a search-warrant being issued for the examination of his room, clothes, and so forth, it was discovered that he had destroyed all his papers, and rearranged all his possessions, on the very afternoon of the disappearance.

The watch found at the Weir was challenged by the jeweller as one he had wound and set for Edwin Drood, at twenty minutes past two on that same afternoon; and it had run down, before being cast into the water; and it was the jeweller's positive opinion that it had never been re-wound.

This would justify the hypothesis that the watch was taken from him not long after he left Mr.
Jasper's house at midnight, in company with the last person seen with him, and that it had been thrown away after being retained some hours.
Why thrown away?
If he had been murdered, and so artfully disfigured, or concealed, or both, as that the murderer hoped identification to be impossible, except from something that he wore, assuredly the murderer would seek to remove from the body the most lasting, the best known, and the most easily recognisable, things upon it.

Those things would be the watch and shirt-pin.

As to his opportunities of casting them into the river; if he were the object of these suspicions, they were easy.