I would argue that total anterograde amnesia would be a serious challenge for sentience, yes.
That's not how we define conscious anywhere.
You can process the world around you, feel and introspect. Even if your judgment is off and you forget your actions, you're conscious in that moment.
From a neuroscience perspective, what you're suggesting is absolutely false btw.
I haven't studied neuroscience so I don't know how you define consciousness. I have read Julian Jaynes's "The Origin of Consciousness..." which in my untrained opinion makes a compelling case that consciousness is a hard term to define.