A second is way too short. Sometimes someone will say something and it'll be minutes before I consciously hear what they said. Auditory (and verbal) processing centers have circular buffers that can hold things for quite awhile. Visual not so much--people only imagine they can hold a picture in their mind.
But, yeah, in terms of long-term semantic and episodic memory you can't retain it unless you were conscious of it. People who claim so-called photographic memory in fact only consistently recall details that they consciously noticed. People with hyperthymesia also only remember stuff that they were consciously aware of.
You heard that they said something though, right? Yes, you might not resolve the sound into words until after working at it but whether the brain promotes the stimulus to conscious awareness and saves it or if the activations fade should be entirely resolved within a few hundred milliseconds. The stimulus has to go superliminal to get into those circular buffers you're talking about, there aren't any buffers that big in subliminal processing.
You're probably right. I shouldn't draw too many conclusions from my perceived experiences. And consciousness is complex enough that I might not appreciate my awareness of the sounds, not to mention my awareness of the elapsed time.
Plus, it's hard to argue against what the research suggests about echoic memory: https://en.wikipedia.org/wiki/Echoic_memory. Minutes is at least at least an order of magnitude greater than what's been shown.
But, yeah, in terms of long-term semantic and episodic memory you can't retain it unless you were conscious of it. People who claim so-called photographic memory in fact only consistently recall details that they consciously noticed. People with hyperthymesia also only remember stuff that they were consciously aware of.