Hidden Texture in 雨のちSweet*Drops PV?

While messing around with the textures in this game, I found this inside pve_11.igb, which itself is located in the DivaDataList.afs, one of the key files in the Project Diva 1st ISO.

This is, as the title suggests, a texture file for Ame Nochi Sweet*Drops. I looked at the PV, but I couldn't see this texture anywhere. No surprise, as this texture would appear very out of place. Rather, it would seem more fitting for Hato's PV, which has a similar texture.



Strangely, this texture wasn't in the same format as the other textures, with it being a 24 pixel bit format RGB image, instead of the 8bit+alpha that the rest of the game's images seem to have.

Maybe I'm just missing something, but if you know where this texture shows up in-game, please tell me! Or, if this is a real treasure map, let's try to find where the map points!