You could make a worm trap. Cut the top off of a bottle and invert it into the bottle and glue it. Put some food in it and set it on the bottom near where you think it might be hiding. You could use like a 20oz soda bottle or if it's huge a 2liter...:(
Like this one...http://www.dailymail.co.uk/sciencetech/article-1165930/Barry-giant-sea-worm-discovered-aquarium-staff-mysterious-attacks-coral-reef.html (scary)