We don’t like to talk about sample sizes in terms of “number of people talked to” since we sample contexts and behaviors in addition to human beings. So an ethnographic field visit with one person might be the equivalent of giving a survey to twenty people or a thousand people for that matter. That’s because each visit contains the potential for a vast army of data points and data sources.
The better question might be, “does your ethnographer know how to utilize this vast army of rich data points?” That said, social researchers and consumers of social research like to think in terms of head counts and so a small ethnographic project might include twelve or so primary participants (along with the people in their social network and the contexts in which the fieldwork took place). Large projects might involve more twenty, thirty, or more field visits (with long interviews and participant observation).