Hey Speed Racer,
Lucky water pumps don't ever fail intermitantly. Your car probably got a little hot because the antifreeze isn't quite full. Make sure your overflow tank is full and it should suck itself full.
I would keep trying to watch for leaks but if that frustrates you go to a radiator shop and ask them to pressurize your system and that will locate the leak. I'm still bettin on a hose.