Was it the engine oil temp, or the engine temp that went high. I am guessing it was the engine temp. I would check the radiator for blockage. Dirt, mud caked up in front of the radiator, leaves, bugs, all clogging up the radiator fins will not allow air to move through the radiator to keep the engine temp cool. Now if there is nothing blocking the fins of the radiator. I would check the fan clutch. A fan clutch that will not engage will cause the engine temps to rise. Because the clutch will not engage it will not make the fan spin faster which would normally pull in extra air and cool the engine down. I doubt it has anything to do with the thermostat, if it was the thermostat it would show the problem more often then this. Also I doubt it is the water pump because usually a bad water pump leaks antifreeze. You did not mention any leaking coolant.
What you have is an air flow problem.