He saw nothing there, nor anything in the low country between, save the rear ranks of the Union army marching on.
But Shepard had been right.

Lee and Jackson, advancing silently and with every avenue of news guarded, were there behind the mountain with sixty thousand men, flushed with victories, and putting a supreme faith in their great commanders who so well deserved their trust.

The men of the valley and the Seven Days, wholly confident, asked only to be led against Pope and his army, and most of them expected a battle that very day, while the Northern commander was slipping from the well-laid trap.
Pope's judgment in this case was good and fortune, too, favored him.
Before the last of his men had left the Rapidan Lee himself, with his staff officers, climbed to the summit of Clark's Mountain.

They were armed with the best of glasses, but drifting fogs coming down from the north spread along the whole side of the mountain and hung like a curtain between it and the retreating army.

None of their glasses could pierce the veil, and it was not until nearly night that rising winds caught the fog and took it away.