You would. The problem is the gravitational effects are subtle, the planet is very far away, and dim. To add to the problem. Objects in the outer solar system

You would. The problem is the gravitational effects are subtle, the planet is very far away, and dim. To add to the problem. Objects in the outer solar system are spread out more vertically in their orbit. ( Like Pluto which dips far above and below the intermediate plane. This means there is a relatively large area of they sky it could be in. Due to it's distance, it is not going to reflect much visible light at all either. So instead of being able to just scan across a the invariable plane looking for it we have to look in a large swath of the sky for something very dim, moving very slowly.