Neither LLMs nor popular search engines return "I don't know" often enough. They will waste your time with bad approximations to an answer instead. But as you s

Neither LLMs nor popular search engines return "I don't know" often enough. They will waste your time with bad approximations to an answer instead. But as you say, "the thing you're asking for might not exist" is useful information, and lets you make faster progress with your guessing, so this compulsion to always supply an answer just slows down the process of getting to a good one.