In a case like this it's plausible that the alternator quit supplying power to the battery. I'm assuming the engine cranked over strong at the beginning of your adventure, so that rules out dirty cable connections.
Driving around on battery power at night only works for a short while until the ignition system and lights drains the juice left in the battery down far enough to kill the engine.
Of course it had to wait until you were in a puddle to cut off the engine. That sounds just right
After you get your battery charged up just put a volt meter on it with the engine running. Should be registering somewhere around 14 volts and will slowly drop down to 13.5 as the battery is topped off after cranking it up. If it's 12.5 volts with engine running then the alternator is not supplying power.