Well, all versions contain the diode but it would appear to depend on whether it is the version 0.9 as illustrated above, where what you refer to as "Vin" - the pin nearest the reset button - is indeed wrongly connected directly to "VDDUSB" and the diode has no function; or the version 1.0 where it connects to "VDD5V" on the "safe" side of the diode.
Or whatever other variant of the NodeMCU you might have. The documentation on the official NodeMCU site is truly woeful and the diagram(s) may possibly be totally wrong.
The obvious first step is to get out your multimeter and test to see whether the diode is between "Vin" and "VDDUSB". Easy enough. 
This is also rather important as in the version 0.9, the CH340 is directly connected to "Vin" ("VDD5V") and connecting it to any voltage in excess of 6 V will necessarily "smoke" it. In the version 1.0, the CP2102 connects to "VDDUSB" instead and the diode protects it from higher voltages applied to "Vin".