This poor guy has had a nightmare with his previous keyholder & I think he's doing the exactly the right thing!
1) Warning everyone to check their holiday homes - check the bills, turn up unexpected from time to time, just make sure the keyholders are not doing anything they shouldn't.
We have a few neighbours in our block who also keep an eye on our apartment when there at Condado and would report back if there was any movement.
2) Sacking the keyholder and moving to someone more trustworthy.
3) Not naming & shaming on a public forum and not going to the Police or any official body.
It's a personnel decision and it's hard to say what you'd do unless you were unfortunate enough to be in the situation, but I agree with Jackinbox. An unoccupied apartment in Spain has got to be an easy target for retribution. It's always difficult to know what to do when you've been wronged, obviously official action would be warranted but most people would rather just move on and not keep looking over their shoulder or worrying about their apartment 1000s of miles away. I would however name and shame to friends, face to face or private e-mail but not on the public forum in full view of everyone.
It seems a lot of posts get turned upside down and every word questioned. Let's give people a break, we are all here for each other (Except this keyholder).