I would do the "+1" indication of agreement to this, but it would need to be more like +1,000,000 to be accurate. Even if by some fluke they're not in the tank right now, just wait - they'll get in there eventually one way or another even if it's as eggs or larvae. Not so long ago I pulled a rather large one out of my thought-to-be wormless tank. Have never seen one in there lights on or lights off in three years!
I have loads in my tank. Some are getting to big for there boots though and coming out when im feeding i have removed 3 in the last few weeks because they was huge. If the worm is fairly small throw him in to do some cleaning for you