Hey for what it's worth, Just did a complete flush of my MN Triton 2014.
Thought while I was at it I may as well do the thermostat too - to my surprise I found a temporary clear plastic blanking plug floating around in the radiator pipe between the thermostat and radiator. Looks like it would have been fitted to the radiator to prevent anything getting inside before fitment to the car on the production line. I'd guess the line operator forgot to remove it before fitting the radiator, and upon first engine crank it probably blew off the radiator and into the pipe. It's diameter is a nice fit, just narrower than the radiator pipe inside diameter.
So this temporary cap has spent 150K's smashing itself against the thermostat, looks like it's had a hard life. Over time it has developed a hole in it which has probably allowed coolant to still flow during the times that its orientation would have completely blocked the flow.
If I was a betting man I'd say there's one reason for a Triton's eventual engine failure due to overheating, I was just lucky to have found it through randomly looking down the pipe while removed from the thermostat housing.
Look out for it next time you do a coolant flush, you never know !