I have not yet talked to Lin about getting Panties. However, it appears talking to Lin about the suitcase is required for the note to spawn. Also, a better hint may be with the Help of Lina's Camera, alter the note.
The in game choice is borrows Lina's Camera. Further, the choice of borrowing the camera does not appear on the flow chart. Last, when I did work with Lina and the camera, the flow chart entry, "The Note's Secret is red although the "borrow camera" is now visible white and the and Altered Note is blue.
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The Heart filled in so the quest is complete. Still have to figure out the purpose and if this is one of the items that seem to transcend time
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it says by will persists.
Quality of life suggestion
Maybe this mechanic can be fleshed out a bit. I as a player am very confused by this ability and mechanic. Don't get me wrong, I am intrigued, but confused and the shear number of flipping conditionals is a heavy cognitive lift