It could be that these people had good intentions, and were depending on someone to care for them well while they were gone. It may not be their fault that the person never showed up. I would just let them know that you became worried, not seeing anyone come to check on them, and what you found. I wouldn't be accusatory because they may have trusted the person to care for them. Some people don't realize how dangerous heat lamps are, and also don't realize that chicken won't move away from them, burning them selves. Lamps should alway be 18-24 inches overhead, and should never be left unattended. You have to live near these people, so you may want to give them the benefit of the doubt. It's just too bad the chickens suffered, and were burned.