Here's what I found at gamefaqs

After saving Balamb Town, you will occasionally find a girl at the entrance of the town or at the train there. Talk to her and she will mention something like, "Hey, zell, do you know a girl at the Garden with a pigtail?" Note that Zell must be in your party. Next, go to Zell's house, and talk to his mom, and then check in at the Balamb Hotel. The next morning, simply search the counter in the hotel to recieve it.