The Day The Magic Died - S5-E15
Visible crew/equipment: While Phoebe and Paige are in the kitchen with the unicorn they realise they've lost their powers, and when Leo joins the sisters in the kitchen we can see two animal handlers - one wearing a short sleeved white shirt behind the animal, and another holding the rope hiding under the table. (00:10:35)
The Day The Magic Died - S5-E15
Visible crew/equipment: While Paige and Phoebe are in the basement getting some magic from the unicorn horn, Phoebe figures out it was the Elders who sent the unicorn, and just as Paige comments that the unicorn's magic is not affected by what happens on Earth, you can see the animal handler's hand under the animal's muzzle. (00:37:35)
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.