The City And The City (China Mieville). Two nations, occupying the same physical area, and occupants of either nation have been trained/socialized since birth

The City And The City (China Mieville). Two nations, occupying the same physical area, and occupants of either nation have been trained/socialized since birth not to see or interact with the other nation. If they do accidentally, for example with car accident that breaches the psychosocial barrier between them, they must 'unsee' it lest they risk an illegal breach themselves. Sounds like the OP was in the United States of Silicon whereas pooping man was in the Democratic Republic of the Tenderloin. His g/f breached instead of unseeing it like any natural citizen of the US would have done.