An Important Observation From Sodom and Gomorrah: Welcome People, Care For Them
We don't know, in this instance, how many survivors were left behind in the cities or in the surrounding areas. And we also don't know whether those survivors were unified enough or resourced enough to go and retrieve Lot and the others. It's perhaps likely the remaining people in this region weren't connected enough to their individual neighbors to even know who Lot was, let alone to notice if he was missing. After all, Ezekiel 16 paints Sodom as lacking much sense of community.
“This was the guilt of your sister Sodom: she and her daughters had pride, excess of food, and prosperous ease, but did not aid the poor and needy.” - Ezekiel 16:49-50