Yoda hit the ground and lay still. He was weak and hurt. Palpatine stood above him cackling. The Force was in Palpatine's favor, and Yoda was beaten.
Palpatine, however, became slient and... fearful?
A familiar presence was at Yoda's side.
"Get up."
He couldn't place that voice, though it was as familiar to him as the Force itself.
"Master, get up. Get up!"
Yoda struggled but fell.
"You must get up!"
He tried again.
"Get up!"
The voice was not harsh but urgent. It swept over him like the Force itself swept through him as the person spoke.
Palpatine stood, his voice quieted, his body stilled. Fear was something he had never felt before in the presence of the person at Yoda's side, but now it had frozen him.
"Get up, Master! You must get up, now!"
Yoda continued to struggle to rise, wondering why the person speaking never made a move to help him. He could not see the person at his side, though he knew they were there.
"If you don't get up now you never will! Get up!"
He finally struggled to his feet. His vision returned, and he turned to his rescuer.
"Tyln."
The ghost of the late Tyln Dooku smiled down at his Master.
"Well done, my Master. New flee while you have the chance. Palpatine is too strong."
So Jedi Master Yoda fled, sensing Dooku with him, protecting him, guarding his Master.