Perhaps he wanted Hawksley himself to inquire about the stones; test him out.

If he asked frankly that would signify that he had brought the stones in honestly, paid his obligations to the Customs.
Otherwise, smuggling; and in that event conscience wouldn't matter; the emeralds became a game anybody could take a hand in--anybody who considered the United States Customs an infringement upon human rights.
What a devil of a call those stones had for him! Did they mean anything to Hawksley aside from their intrinsic value?
But for the nebulous idea, originally, that the emeralds were mixed up somewhere in this adventure, Cutty knew that he would have sent Hawksley to a hospital, left him to his fate, and never known who he was.
All through the narration Hawksley listened motionless, with his eyes closed, possibly to keep the wavering instability of the walls from interfering with his assimilation of this astonishing series of fact.
"Found you insensible on the floor," concluded Cutty, "hoisted you to my shoulders, took you to the street--and here you are!" Hawksley opened his eyes.

"I say, you know, what a devil of an old Sherlock you must be! And you carried me on your shoulders across that fire escape?
Ripping! When I stepped back into that room I heard a rushing sound.

I knew! But I didn't have the least chance....

You and that bully girl!" Cutty swore under his breath.