Unfortunately, the answer to this is entirely unsatisfying.

Two men of the 27th Indiana, Sgt. John Bloss and Cpl. Barton Mitchell, discovered the envelope with the three cigars, around which was wrapped “Headquarters, Army of Northern Virginia, Special Orders, No. 191". They had enough sense to know this might be important, so delivered it to Capt. Peter Kop, who in turn brought them to Col. Silas Colgrove, and from there, the paper was sent to Col. Pittman, the Division Adjunct, and then Gen. Alpheus Williams, commanding 12th Corps, and then to McClellan himself.

Bloss and Mitchell were brought along as far as Col. Colgrove, at which point they were sent back to their unit. It seems apparent that they were not returned the cigars. The closest thing we have to any clues is that Mitchell, later recalling the discovery, remarked "As I read, each line became more interesting [and[ I forgot those cigars". As Stephen Sears puts it in his book, "who finally smoked them is lost to history." Possibly someone along that chain of custody was the one, although it could have been one of their aides, or perhaps they simply were tossed in the excitement. You are welcome to speculate!

See: Stephen Sears' The Landscape Turned Red or James M. McPherson's Crossroads of Freedom: Antietam