Ah, yes. This is a very common issue. Members learn that if they put water on the temperature sensor it will trick the steam generator into thinking the room is cooler than it really is and produce steam. Eventually this abuse will burn out the temperature sensor, take the room down and a repair is needed. This is also dangerous in that they can overheat the room.
When the room is down because it can't regulate proper temperature anymore, these abusers are the first to complain.
We have a temperature sensor cover that will aid in deterring this behavior. Also, installing a globe valve as a regulator will allow you to dial the steam into the room as a slow constant as opposed to large bursts.
Check out these productsTemperature Sensor GuardRegulator Valve