I doubt whether it had all that fluid in the crankcase for 4000 miles.
Most likely, the coolant was sucked in all at one time which caused the engine to shut down.
There may have been a momentary spike on the temp gauge.
There would have not been enough time for coolant and oil to mix enough to get the milk chocolate look.
I think the 4,000 mile drive is misleading everyone.
This condition was sudden. Hence, the appearance of the oil.
The coolant should have been low after shut down, if this is 'in fact' what occurred.
I have seen engine oil when coolant was sucked in thru the intake manifold (3.8L GM)
and the engine oil did not have enough run time to mix thoroughly.
When the oil was checked, it appear several quarts above the fill line, but the color still looked right.
A good mechanic would immediately 'pick up' on the 'feel' of the oil - not right.