You know, I've just realized something. The Pokemon thieves in the show, even the supposed professional J, are complete idiots. They have no idea of just how easy stealing could be with the right Pokemon. For example, train a Psychic type to know Teleport and Confusion. Stake out your target human, and when they recall their Pokemon, have the Psychic type Teleport in, use Confusion to grab the balls, and then Teleport out again. Bang, you've just stolen all their Pokemon, and they can't give any description to the police that doesn't fit every other member of the Pokemon's species in the world. And they can't track you, because the Teleport could have gone anywhere. Another example, train a Grass type to know Sleep Powder. Stake out the human and when all their Pokemon are recalled use it on them. Steal everything before they wake up.