Bro is in state called shock and panic
Shock and panic generally causes freezing, not memory impairment. This is proven by the fact that he remembers the person having golden eyes and their physical build despite how dark it is---and is actively trying to remember. If he had forgotten their voice, he would've forgotten other aspects too. For humans, fear triggers stronger retention than anything else. We remember better the things we hate, both consciously and subconsciously. In cases of severe ptsd and physical trauma, yes you can forget; but you typically forget everything associated with, not some selective aspects of.
You may have missed the time jump. He might be too panicked in the moment but if he hears the voice after the assault again he probably will connect 2 and 2.
Idk why I read this except morbid curiosity...but anyway, I'm surprised he can't just recognize them based on voice...??? Like even if you can't see, they're talking full blast???