This is addressed with a little more clarity in the screenplay and novelisation.
Jim Gordon had the draft speech (which he decided not to give) in his jacket pocket. One of Bane's men finds it and hands it to Bane.
BANE: Search him. Then I will kill you.
[The Thug, terrified, pulls out Gordon’s badge, wallet, gun … and the folded papers of the speech he did not read. Bane takes these one by one with quick glances. He stops at the papers. Unfolds them...
As he reads, Gordon rolls off the steps, dropping into the rushing flow of water – gunshots ring out...]
THUG 2: He’s dead.
[Thug 2 trails off as Bane looks up from the papers...]
The man held onto Gordon’s gun for a moment longer before meekly
surrendering. He put it down, and a look of mournful resignation came
over his face. Rummaging through the prone officer’s pockets, he took
out Gordon’s wallet, badge, and several folded sheets of paper.
My speech, Gordon realized with alarm. Dear God, no…
The doomed felon handed the items over to Bane, who briefly examined
them, one by one. They appeared to be of little interest to him, until
he came to the papers. He skimmed the pages quickly, then paused and
read through them more carefully. His eyes narrowed.