Live and learn, Spencer. With auto electrics, the ground is always negative and is "grounded" to the chassis. One German vehicles, the wiring color code for the ground id always Brown. The "other" wire is +12v and is "hot". THE BIG EXCEPTION being British vehicles in the 1960's and earlier. The Brits, being typically contrarian, adopted a "Positive Ground" standard. Ack basswards.
Incandescent bulbs don't care about polarity (which end is positive and which end is negative), but the sockets can. The shell is always the ground. Motors care about polarity. LEDs care about polarity. Electronics care about polarity (and be careful, you can let the Majickal $moke out).
No playing around with Mrs Fish to get hotness back til you get (this problem with) the bike straightened out.