Just got done analyzing last night's battles (I know, it's been a busy day for me).
There is definitely something strange about that Charizard. Renata's Ampharos should have had a good, bordering on unbeatable chance of victory, since electric is super-effective against flying, and flying is not very effective against electric while fire is only moderately. In fact, chaotix points this out for us.
"As soon as it was instructed, Charizard gave a great flap of its wings, stood its ground, and instantly broke the electric current. It hardly looked fazed by the super-effective electric attack, and with a devious glint in its eyes it launched another Fire Blast."

I think if and when we find our Charizard owner, it will be time for a uni-boot, especially given the "The opposing trainer did not look as if to have any intent of ending the battle with just the Pokemon" clause. By contrast, I'm going to guess for the moment that the Magnezone owner may be a vig, based on the not-killing of Nurse Joy.

If the attackers use up their pokemon and don't have extras, then there's a good chance Maxie's attacker is completely vulnerable if discovered, because he lost two last night and may well have been one of the attackers the first night.

The other question is, we had three attacks both nights. If the charizard attacker attacked on the first night, why didn't they use charizard then? Granted, it's perfectly reasonable that one of the attackers from the first night wouldn't have attacked again, not wanting to risk the loss of more pokemon.