I've read on many websites throughout the years that Middle and New Kingdom-era Egyptian soldiers often utilized a thickly padded, triangular-shaped groin armour. Most of the time, modern depictions of this armour portray a soldier as ONLY wearing this one piece of kit with nothing defending his torso or head. It seems strange to me that rank and file ancient Egyptians would neglect all vital organs and only protect the groin (obviously, we know that many nobles and kings wore full body defenses of scale et al., so this does not apply to ALL ancient Egyptian warriors). Is there any historical evidence that shows that this is the case? What historical sources do we have that tell us when, where, how, and by whom, this particlar padded groin armour was used?

There was no Egyptian groin armour. It was just someone's dodgy interpretation of a kilt or loincloth illustration that was repeated by other authors who didn't bother to do their own research.

This book might help ;)
http://www.myArmoury.com/talk/viewtopic.php?t=26686

That is precisely what I figured would be the case. Also, I definitley plan on checking out the new book.