It takes 4-5 miles of driving to get any cabin heat. Anyone else have this problem?

Thanks! I stopped at the auto parts store yesterday and picked a thermostat and gasket. They didn't have anything special listed for the hybrid highlander. I did a quick look under the hood and didn't readily see where the thermostat might be. Normall I expect to find them on the top of the engine where the hose goes to the radiator. Do you happen to remember the location?