Why is my drain circuit always drawing current, regardless of MOSFET gate state?
Thank you to those that provided their feedback in the comments to my question above.  I've learned a lot more about how MOSFETs work, and also got some hands-on testing experience.

I built a simple test circuit (below) to demonstrate any failure of the component.  In doing so, I removed the micro-controller and Buck converter to eliminate any bias that these components may introduce.







simulate this circuit &ndash; Schematic created using CircuitLab

Clearly, there should be no signal to the gate channel when the circuit is energized.  However the LED illuminates in this configuration, and becomes only slightly brighter when the push-button is closed. In the open-switch state, Vgs is ~2.5V and I don't think that can come from anywhere other than an internal short/failure.

Here's a photo of my breadboard showing an implementation of the circuit.