"Hermione's white face stuck out from behind the tree" most clearly tells me she was seen because she is pale and the night is dark and her head was sticking out from behind a tree.
Yes, you've made it very explicitly clear that's what it says to you. Don't worry. I didn't fail to understand you.
It does little to imply fear in that sentence.
To you. To me, it very much implies fear.
Rowling forgot she wrote that little sentence, and made a declaration that Hermione is raceless in the book, when had she really envisioned a non-white girl and envisioned the scene in actuality, would have come to a different description.
If your position has fallen to inventing what an author does or does not remember or envision, in contrast to what she actually says, I don't really see the point of this conversation.
It may be perfectly cromulent, but the glove does not fit. the probability that an author would describe a black character hiding behind a tree with their head sticking out as "white face" would be one of ignorance to the actual visuals of the scene.
Basically, go get a white and black friend, wait until night, and take some pictures of them hiding behind a tree with their head sticking out. Heck, film it. Then draw a gun on them, to get the blanched fear look.
Pretty sure you won't be using the word "white face" to describe the black friend (even without the gun, that's just dangerous), except to be contrary.
You're confused. It's a perfectly common phrase used to describe fear. The fact that it's not familiar *to you personally* is completely irrelevant.
But this is getting silly now. I've no intention of repeating myself over and over, or responding to the same posts over and over, and clearly you're not going to be convinced, so I'll drop out of the debate having made my position and opinion clear. We very much disagree on that particular quirk of language, and what it means.