Hmm depends on what the intentions of the trainer's
If it was an accident or the trainer didn't knew what that was and thought it was a cool toy than he's innocent
But if the trainer wanted the full deck that that really depends on what the trainer did before
And if the trainer did that with evil intentions. The trainer sucks
Ooh, I've seen this comic, I'm pretty sure after that the flareon keeps trying to hide firestones everywhere so eevee evolves, but he's too smart for it