It's hard to tell from the photo what happened...is that a branch that snapped off completely? I can't see the bottom part. Or is it still attached to the plant?
I've nothing helpful really to add, I would agree, use root hormone and plant it. I have harvested a broken branch in a very similar state (it got bent moving it and failed to recover when tied with wire), and it was so weak in THC it wasn't worth smoking, hardly any trichomes and they were all clear.