The novel did say that Strategist Liu was captured when he was scouting the enemy. The exact detail was not provided because the real Wei Xiao Hua didn't leave the capital city again after the temple incident because it was the time to settle scores with her family members.
But….
"But he's safe?"
"Yes. They said that one way or another, Strategist Yang save him," Prince Ji Shu replied.
Hearing that, Wei Xiao Hua blinked her eyes a few times. She had thought about this a few times in the past, but she didn't expect that it really would be that way. Based on the story, Strategist Yang would make a critical mistake and lose miserably. Because of that mistake, Strategist Liu died in the battle, making Strategist Yang in despair…