Drawing a line over video that is camera tracked Complete noob here with After Effects but I feel I am so close of achieving it yet... 

I am trying to draw a line using the pen tool and get this line to follow along with the camera movements. Something like this:


I have created this using Track Camera on the footage, then selecting a target, right click and create null object. Then I draw the line on the null object using the pen tool, so it creates it as a Mask. All I want is that mask to stay in the footage, no effects, nothing special. Just this yellow line. 

So it does work fine if I have the mask selected and I play the footage, but it disappears when I see the video from Premiere (they are linked) 
What am I missing? 

Thanks!
Masks do not render in after effects, the lines and boxes are UI elements of the program. To render a mask you have to apply an effect such as the stroke effect to the layer, using the mask as the source.

You could also add a stroke as a drawing on a new layer. You can do that by using the pen tool when there are no layers selected. That will create a shape layer with the current fill and stroke settings, so you may have to turn off the fill.

The boxes around the points would also have to be drawn as individual elments. You could use the square shape tool to draw them as either a source for the stroke effect or on the shape layer.