NPN transistor energy drain from base to emitter?
You mean there is no supply at the collector! The emitter is the pin with the arrow however, it matters not because, you can put a meter on a transistor and find a diode between collector and base and emitter and base and this is why your LED lights.

Current from the +5 volts passes through R1, passes through the base-emitter diode and then onto the LED (which it illuminates).