If someone in their community has a full copy – they can ask them, and that's as far as the query needs to go. Or, you can keep asking less trusted servers until you find your answer. If you're in a conflict zone and you want to find someone controversial, this is important.
But no one is going to let you scrape the DHT to provide this kind of plausible deniability because query scraping is the kind of spam the DHT is supposed to keep out. The only way to get a full, private copy is if the system is designed around the efficiencies you gain from putting things in chunks