One possibility is that the engine DID become very hot while driving. When you stopped the engine, the water pump stopped circulating coolant and the engine fan was unable to cool the antifreeze then residing in the radiator. The residual heat from the engine caused the cooling system to overpressurize and release pressure and coolant through the hose.

Another possibility is that the transmission became very hot, and the high transmission fluid temperature contributed to the coolant release. The factory transmission cooler runs a line through the radiator.

If you don't have one already, I would consider adding an aftermarket transmission cooler to your truck. Unless those horses are on a diet, you're giving this truck a heck of a workout, particularly in this weather. Excessively hot transmission fluid can change properties and damage a transmission. $$$