I have not heard of the computers being relocated on the '03 trucks but you could check the driver's side kick panel as well to see if it is there. I do know that '97-'02 are on the passenger side and the pre '97's are on the driver's side. Also if you don't find it on the driver's side, you could look for a big group of small wires going through the firewall somewhere. Not far behind that will you find the computer and it's code. I wonder if they may have moved it behind the glove compartment or higher in the dash somewhere. Please, let us know where you end up finding it for sure.
I found this after searching a little in the Chips and Programming forum here.