Hunter, the engine is a 6.7 turbo. This problem can occur at any speed with varying loads.
The engine continues to run at idle,the accelerator pedal has no effect so the truck 'coasts'.
While coasting,shifting to neutral then immediately back to drive results in power immediately restored.This problem may not occur again for many miles (>1-2K)
Internet searches have come up with many diesel problems ( relating to pollution controls), but none like this one.
Your suggestion sounds as plausible as any so I will start with fuel filter replacement and
fuel pump testing and maintenance.