Can't lookup Node by id

I have a node: stepDropper
I've set an id: stepDropper.setId("STEP_DROPPER")

The node is added to the Root node of the Scene.

I call scene.lookup("STEP_DROPPER") at runtime - I get Null result


The same scenario works if I set a CSS selector:
stepDropper.getStyleClass().add("STEP_DROPPER")

and then I call scene.lookup(".STEP_DROPPER") - I get the Node itself