Here's an over-view of the SS quest; read it over and try to find something you might've missed.
It might not be 100% but I'll try to minimize the spoilers
One you talk to the man at the Bazaar or the Lady in the Knight Academy Kitchen, go to bed and sleep until night.
Go to the BOTTOM floor of the academy. The Toilet should be around, between the double doors (that leads to outside the academy) and the Kitchen.
If you found the right door a sequence should activate where you can here some 'haunting sounds' (The crying lady/Hand).
A text box should appear when the hand in the toilet starts talking to you (If this doesn't happen try opening the toilet door). After to listen to/read everything they have to say, go to bed and sleep until morning.
In the morning, Cawlin should be standing on the bottom floor of the Academy where the Double doors are. Talk to him and it should activate 2 Sidequests.
You can either fulfill Cawlin's request (Love-letter Quest
) or for something else (Toilet-paper Quest
). Using the item Cawlin gives you, you can either activate 1 of the 2 quests! Mind you, once you have activated one, you can't do the other, so choose wisely! Either way, you will get the same reward for either.