What happens is that Riboku comes back, defeats Kanki so badly that Kanki and his whole army flee Qin, and then Riboku proceeds to hold the line against Qin for the next few years. Then the Qin use Zhao spies to convince the Zhao court that Riboku’s aim is to become the King of Zhao, so the Zhao court themselves remove Riboku from battle and execute him, while dismissing Shibashou from service. Zhao itself falls shortly after.
another version I read is that after Kanki loses first he participates in the next war and then Riboku actually kills him.