head unit switch/constant wiring

so my brother had his friend check out my wiring and his friend ripped my perfectly soldered wires apart connecting the switched wire from the head unit to the switch wire of car, and the constant from head unit and the constant from car.  I guess his friend thought it would be cool to be able to have your cd player on while the keys are not in the ignition and possibly drain your battery!  Well after talking some sense into my brother I went ahead and fixed my wiring back to the way it is supposed to be and it did not even turn on.  I don't know if the cd player does not recognize the switch wire coming from the car now or what, but it does not turn on.  I had to wire it back the way his friend did just to get it to work again.

Anyone have any ideas why this would happen and maybe how I can fix it?

thanks