That's a major bummer. I am really surprised that the starter wasn't the problem. If there is any such thing as a "bright side", to what has happened, it is that you have eliminated the starter and the battery from the equation. When you have relaxed a bit and feel like trying something else, there are a couple of things to do. Something is interrupting the circuit, either on the power side or ground.
There are two relays in the start circuit. The BCM signals the Run/Crank relay to close, which provides power to the Start Relay. The ground for the Run Crank relay is G105, the infamous little black box, on the fender wall, aft of the battery. If you aren't familiar with it, let me know and I'll post some pictures.
The Start Relay is grounded through the PCM. There is less chance that the problem is there, but the ground for the PCM is on the left side of the engine block, just forward of the Crank Position Sensor, below the starter.
For the power side of the circuit, try replacing the Run/Crank and Start relays or swapping them with other similar relays in the box.