Actually, the modern meaning of red herring stems from fox hunting. Farmers who were tired of having the dogs & horses tromp through their fields after a fox would set out pickled red herrings. The scent was so strong that the dogs would lose the fox's scent, & the hunt would hit an impasse.

On topic, I would have to suggest Will O' the Wisp as well. Non Sequitur would also work, but to me it doesn't imply a sense of misdirection that Will O' the Wisp does.