Perhaps because it was so terse; perhaps because it was so characteristic.
Dear Mr.Gryce: I do not presume to dictate or even to offer a suggestion to the New York police, but have you inquired of the postman in a certain district whether he can recall the postmark on any of the letters he delivered to Mr.Adams?
A.B.
His, on the contrary, was perused with a frown by his exacting colleague in Gramercy Park.

The reason is obvious.
Dear Miss Butterworth: Suggestions are always in order, and even dictation can be endured from you.

The postman delivers too many letters on that block to concern himself with postmarks.

Sorry to close another thoroughfare.
E.G.
Meanwhile, the anxiety of both was great; that of Mr.Gryce excessive.
He was consequently much relieved when, on the third morning, he found Sweetwater awaiting him at the office, with a satisfied smile lighting up his plain features.

He had reserved his story for his special patron, and as soon as they were closeted together he turned with beaming eyes toward the old detective, crying: "News, sir; good news! I have found them; I have found them both, and by such a happy stroke! It was a blind trail, but when the florist said that those petals might have fallen from a bride rose--well, sir, I know that any woman can carry bride roses, but when I remembered that the clothes of her companion looked as though they had just come from the tailor's, and that she wore gray and white--why, it gave me an idea, and I began my search after this unknown pair at the Bureau of Vital Statistics." "Brilliant!" ejaculated the old detective.