Thanks, y'all, for all your good advice, and sorry I've been absent. When it comes down to it, I think part of what bothered me about this scene is not just that the fake-death is obviously untrue, but that it's also... not truly necessary here. You've all said very good things that all tend toward, let's call it the centrality of this event, but the truth is in this moment of the story his fake-death is not central b/c I've got something more central. (Namely, when he reappears, he reappears animated with the extreme desire for vengeance on a certain traitor, and this begins to seriously drive the plot.)

So I should cut the fake-death. All I really need for that moment is fear and uncertainty. His side lost a bloody battle and she doesn't know where he is--that's plenty. What made me want to take it further was how well these words ring as the chapter's ending:

His eyes grew dark with what she could swear was pity. “You don't know?” he said gently. “They shoot their prisoners. Every time."
BUT I don't need things to be clear-cut in order to have this line. She knows how badly the battle went... she asks the survivor she found for news of the men she knows, he knows nothing except it wasn't looking good last he saw them... she asks what happens to prisoners. That'll do.

Again, thank you all.