Did you activate the option "TRAILS" in your graphic options (in game)?
If not, just do that:
Open Toribash, Press ESC, Click in SETUP, OPTIONS, ADVANCED (in the bottom part), and there you will see a box called "Trails" check it if is not checked.
Did you activate the item? Click the "Shop" Tab on the top of the TB page, look for a button called "Deactivated" Click that button. You should see a trail if you haven't already activated it, So click "Activate" On the trail, and it should move to Activated. If it still doesn't show, check if you have the Trails box checked in your Toribash game.