Do electric worm prods use any electricity (measured at the meter)?

I used to know some old guys that gathered night crawlers using electric prods at night. Their electric prods were plugged into the outlets outside a public school building, and involved running just one wire (not 2! not 3!) from the outlet to the prods - the moist earth provided the ground, and the worms came crawling up. (Sometimes if you grabbed one too close to the prod, you could feel a little tingle through the worm.)

These guys were getting worms from public school yards, because those yards had the nicest lawns, and the most worms. I told these guys they were stealing electricity from the taxpayers by doing this. They told me that since they were only running one wire, and not using the electrical ground/neutral in the meter, that the school wasn't being charged for the electricity, either.

I realize this sounds unethical, because obviously the power company still has to generate the power, but were these guys right? Did the meter really not read that current?

Thanks for your answers!