I would say he gave enough clues to that.
1. 14 RP with all girls pretty much means that line is in some scene with all girls present (why the hell RP check with all of them then?)
2. Money check means the line is in some scene with purchasing (again why the hell money check if not?)
3. DIK choices just a filler
4. DPC sure nobody seen the line cuz the line must be somewhat out of blue. The one who saw it definitely would ask about it somewhere.
The only one left is to combine the clues
Maybe somewhere during freeroam before second DnG game? All girls present, you can buy from Magnar