Penumbra Overture Note's Found

[Ashtoreth]

Hi guys! I know this topic is old, but I thought it would be better to post here than to create a new thread, because my question is related to Penumbra Overture's notes.

Spoiler below!

I was wondering if anyone knows where can this note be found at. I've finished the game with 23 notes found, but apparently there are 24 notes.

Thanks : )

Edit: Added spoiler tag.