Another brain teaser?

You turn two of the switches on for 30 minutes, then turn one of them off so you still have one turned on. You go into the room straight away, and if the light is on, the switch you left on is the right switch, if the lamp is off then you feel the lamp if it is hot, then the switch you just turned off is the right switch, but if the lamp is cold then the switch you haven't touched is the right switch.