I assume your car was on level ground.....the usual rule of thumb is that if the fluid level is on the hatch section, you're OK. If it gets low again, you might want to look underneath the car to see if anything is seeping out at the pan or if the rubber lines from the radiator and/or cooler are in need of replacing.
Always start with the easy to check things first. Half the time a problem is easily fixed very cheaply. It's when someone has something wrong that they aren't sure of and start throwing parts into it that it gets expensive, and usually those parts didn't need to be replaced.