How many milliamps current did it draw? Alternator will draw some by design but not enough to drain your battery for many days.

That plug is for the alternator Signal and Lamp wire (LS). But both are fused, so if you pull the lamp fuse and the alternator fuse it shouldn't occur.

Tommmo was refering the big red/white wire on the altnernator which is unfused, and it a diode protected form draining your battery.

Replace the alternator to test. I have one you can borrow, i'm in the Eastgate area.