Does anyone here happen to know right off-hand where the painting for this side mission is? I could swear that I've checked everywhere in the gallery, aside from the area where you overhear Carol and Diane talking in the one cutscene, as I'm unable to go there. Help! :)

Go to Muses Gallery when Diane is not in her office area, at 15:00. She will
give you [Quest 02: Guardian of the Art Gallery]. Go to the north outside area
(the map shows stairs on both sides, the east side of the map). Climb up to the
window, then look through and shoot the lock off of the door. Go back inside,
and enter the door you unlocked. Pick up [The Girl in the Woods] and return it
to Diane. She will give you in [Trading Card 05: Diane Ames] return. 
 
 

Hahahaha...wow, clever! Thanks! XD

No prob. I figured I should reference my source.

Weird. She ran into her office, and I can't give the painting to her. I suppose that I'll hafta wait for her to come out again...