When you draw with a model line it goes on to the workplane specified, so if you are in a floor plan view it will be drawn on the level of that floor plan unless you chose a diff. workplane. you can select any workplane to draw on, so in a 3d view or elevation view, click the plane button and select a face to draw on, then the line goes on that face. You should be able to copy your line up or down, then delete your original. If not you can copy paste it to a new workplane by copying the object, then set your workplane and then paste align.
