I’ve heard of this, people who do not have a mental illness having heard a voice or two in the past. Long before my onset of schizophrenia I had only heard a voice in my head maybe three or four times in my life and it was a pleasant female voice that would softly whisper my name, just once. It would happen maybe once or twice a year, a handful of times at the most.
So when during a family get together my uncle asked if anyone else had ever heard a voice in their head I said yes I have. He then told me that he had only heard it once in his life and that he was walking down the sidewalk late at night when he heard a voice in his head whisper “Look out!” and as he looked behind him he saw a car careening down the sidewalk towards him. He credits this voice for saving his life but had never before or since heard a voice in his head.
I’ve also heard of otherwise mentally healthy people having experienced other sorts of hallucinations, tactile or whatnot, but only once or twice in their lives…perhaps these things can simply be part of the human experience but occurring only rarely in people not effected by mental illness…who knows really.