This speculation was originally posted on a thread on the saddest ending we could think of for Matt Smith’s Doctor.
He finds out that silence will “fall” on the “fall” of the 11th because his fall through the timestream has altered his face so badly, nearly showing his skull, and hurt his throat so that he looks like a Silent, sounds like a Silent, and is actually the inspiration for the Order of the Silence to mutilate their bodies so (they’re an order, not a species).
With his history with the Silence and the Whispermen, he screams.
Nobody recognises him, friends or enemies. Nobody remembers him after they turn their gaze, even the TARDIS ignores his commands because despite the mental link, every time the smallest thing happens, it forgets what it was doing and attacks him like he was an enemy that devoured the Doctor.
In his despair he eventually manages to revisit the only friends bright enough, brave enough to understand and handle the situation – Vastra & co.
Arriving, stumbling and broken to Vastra & Jenny’s doorstep for refuge from a world that finally truly forgot him as he once wished, Jenny then, after the events of Day of the Moon, shoots him on sight.
And promptly forgets.