Depending on the decision you make at Yureyu to either battle Sigmund or Sirius, and then the decision to make at the Belrose house (go upstairs or downstairs if you battle Sirius at Belrose, or stop the doctor or Sirius), a different character or set of characters will be kidnapped. Possibilities:
-Laura
-Charlotte and Shelly
-Saphira
-Noel and Anna
On my second playthrough I intentionally went with the twins being kidnapped because it's the only route where you don't lose relationship points with any characters just for the situation turning out like it does.
I had some spare time on my hands, so I checked. Ice Cream Sand Witch's original sidequest post was on page 71, so it was a good guess BRS swag. Some other users added to the list, but I didn't want to patch it all together, since it felt like taking credit for someone else's work.