In this situation, it sounds more like a short circuit.

It is critical to distinguish the difference between cranked engine but it won't start and could not crank the engine at all. If you have a drained battery, you would not be able to crank the engine.

What was exact symptom you had when "the engine can't be started again?" Did you hear engine cranking or just a tiny click or even no sound at all?

Drained battery is not a very precise term. Normally, a drained battery means the battery is just not powerful enough to crank the engine, but it still has some juice to power small electrical devices such as a radio (or ignition system). Of course, a completely drained battery will not be able to do anything, even to power the radio.

Once your engine is running, the ignition system has electrical power from two sources: battery and alternator. Under constant charging (when engine is running), the battery should be able to provide a very stable (very small) current to power the ignition system. Since alternator puts out much more current than the ignition system needs, the engine should not stop due to a drained battery.