Thank you @JEPA and @Kony. I now understand what happened to me. I would guess that it's okay to use loops as long as your work is policed on YouTube by a company like Muserk. That way your music is safe and you might also get to monetize the work of other musicians. I do think that this info should be more widely disseminated. While individuals may have little power, companies like Loopmasters, Splice, Big Fish, Zero-G, Native Instruments (sounds.com), Noiiz, etc., might not want their customers to know this. They should work with YouTube to protect all their customers from spurious claims.