User blog comment:Miskos3/Fairy Tail Episode 215: The Snake Charmer Ophiuchus, Review/@comment-3285005-20150110113922/@comment-7418318-20150110115824

The whip is not a mistake.

At some point early in the KotSS arc, Lucy's original (light-saber-style) whip doesn't work, so Virgo takes it to the Celestial Spirit World to either upgrade or replace it.

Now, at least in the anime, it looks like a regular whip until its magical abilities are activated.