If you believe in the theory, then there are dinosaurs still around today in the form of birds.
And there are remote places in the world that humans have barely explored, if at all, unless I am mistaken. If any dinosaurs like a duckbill were to still be around they would probably be in these remote regions. If any dinosaurs are still around, I would have to say that a duckbill would be the most likely candidate, seeing how they were probably the most successful dinosaurs, the most diverse.
I don't completely dismiss the idea of dinosaurs (not the flying feathered kind) still being around. After all, there have been cases of a species thought to be extinct, and then someone finds a living specimen. One example is the coelacanth.