So I was looking for the Persona required to get Snow Queen Whip in List of Persona 3 Items, and it was Skadi. I fused Skadi, and then went to the Antique Shop, aaand it didn't work. I did some research and found this:
turns out Snow Queen Whip is exclusive to Portable, but the wiki still says it's exclusive to both Portable AND FES. It has the † sign to signify it's exclusive to those two games, instead of the ‡ sign to signify that it's Portable exclusive.