Lots of possible reasons unfortunately, were you standing for a long time and did the engine overheat? Might be worthwhile checking the radiator fan comes on when the car is stationery and not getting any airflow through the radiator. Check the coolant level and also the oil for any signs of water in it. Other than that if all seems ok now just assume it was a glitch somewhere and just drive the car. If is was a fault it will probably occur again and you will have to deal with it when it does.
One thing I learned a long time ago is that it is pointless looking for intermittant faults when they were not occuring.