thermostat guard picked open
double wafer lock
Honeywell Thermostat Guards CG512A1009 & CG511A1000
Available Here: www.honeywellconsumerstore.com www.honeywellconsumerstore.com Thermostat Guard protects thermostats from tampering in commercial ...
ControlTemp Product Overview
lock box, thermostat covers and thermostat guards to control utility costs. ... "tamper proof thermostat" "thermostat lock box" ...
In a way with the person wearing a security guard uniform over the thermostat. I'll take the batteries from her flashlight. 
Dnt let negative people alter ur mood!! Guard ur heart! Who's Changing Your Thermostat? / 
Thermostat Guard Box with Key Lock: 
Honeywell CG511A10 reviews 
@ the guard was able to get the aircon on eventually. Dunno if it was overriding the thermostat though.