2003 Buick rendezvous radio 12V ignition/Acc pin not supplying voltage.

I got an after market radio (Dual XTM265) along with a wiring harness for a
Buick rendezvous 2003.  A few days ago, I tested with a multi meter, the pins
that plugged into the previous radio to figure out which one was the
ignition/acc.  I found one that was 12V when the key was turned and was not
when the key was off.  I'm assuming that's the ignition/acc pin, so I adjusted
the wiring harness to match.  I turned on the car, and it worked! however it
was dark and late at night so I didn't actually put the car back together.  This
morning, I put the car back together only to find that the radio didn't work.  
After taking the dash apart again, I found that the pin previously identified as
the ignition/acc pin was not supplying any voltage when the key was turned.  
The General power directly from the battery is working however, so this
leads me to believe a fuse is blown.  I looked at several fuses that I thought
might be the correct ones however I found noting.  I only know what I
learned about cars during this process so I have no clue where to look next.  
Does anyone have any ideas as to which fuse might be blown or where to
look to find the problem if there isn't a blown fuse (I really hope its just a
blown fuse)  I have no clue what would have changed in the past couple of
nights, the car was off the whole time and locked.  Thanks in advance for
any help.