@JoAnn3 Airbnb takes privacy violation complaints very seriously. I realize you didn't enter the guest space, and your actions had to do with safety. But there were things you should have done a little differently.
You should have sent the guest a message saying that you happened to notice the red light as you were passing the window, that told you they had left the heater on when they went out, ignoring your instructions to turn it off. That this is a fire hazard, so since they weren't home and didn't answer their phone when you tried to reach them, you didn't want to intrude on their privacy by entering the unit, so you turned off the electrical breaker to their room, and to let you know when they are on their way back, so you can turn it on again.
If you send a message like this, it is documented for Airbnb to see should the guest raise a complaint.
The infrared heaters I am familiar with have a thermostat, so they won't get any hotter than the temperature they are set at, so they shouldn't be a fire hazard- does yours not have a thermostat setting, or is it just on or off?
And the infrared heaters I know of don't even get hot- the idea of an infrared heater is that it heats the objects in the room- it doesn't get hot itself like an electric heater does.
You didn't need to talk about the detail of the heater incident in the review, either. All you needed to say was that the guest ignored house rules, leaving lights and heaters on 24 hours, day and night, even though they were out almost all the time.