HitFilm masks do not lock onto tracked footage.

Hello,
I have a quick question about HitFilm. I just followed the Mocha in HitFilm tutorial and I successfully tracked the footage. While adding an effect to my tracked footage I have one slight issue. I added a duplicate of the media I tracked and I masked a wall out of the scene. Then it does not lock onto the tracked footage to keep my explosion effect from going behind a wall in the scene. Is there any way to keep the masked media tracked to my project? 
Thanks in advance, 
TechnologyGuy