That we've seen. That doesn't really mean it can't happen. After all we haven't found the end of it yet. Which would be the coldest. And we never will.
Absolute zero is only a theoretical temperature. Like I said, our current understanding is that it can't happen. If we were to witness absolute zero it would force us to rethink certain areas of physics. It's not about where we look. It's about the laws of physics as we've defined them essentially not allowing it within our universe.