In the Anime when the Knights got to Presia's place, Presia told them she'll make weapons for them, but for a cost. Having no money, Hikaru reached in her pocket for anything of value, but could only find a sweet. She offered it to Presia, who told them what she really wanted them to get her the minerals for making the weapons. Anyway, Hikaru ended up giving her the candy anyway.
The question comes up when the Knights went back to Presia, she was killed in the battle with Atalante, one of Ascot's summon beasts. While Presia was about to loose it, she told Hikaru she really liked that sweet. Hikaru quickly told her she got another one of those and searched for it. However, Presia died before she could find it.
So the question is, where did her second sweet go? Some people pointed out in the Manga, Clef was fiddling with Hikaru's skirt (read Clef? Hentai??? for more information) when they first met, and that made the sweet fall out of her skirt. However, this only happens in the Manga, hence not making sense since the sweet business was from the Anime.
The answer to this riddle was Hikaru never lost it! The proof? At the end of the episode, they dug a grave for Presia, and Hikaru placed the second sweet in front of the grave ^_~