Where Did My Money Go?

I could have swore I had over $100 on my Thursday when I ate lunch. In fact, I know I did because I thought I made money on my last transaction by holding up 2, 5000 yen bills. Today when I went shopping in Nakano, my wallet only had 2000 yen in it. How in the world did I spend over 8000 yen in two days? I went straight home Thursday after class, but stopped by the supermarket to pick up some groceries. I must have spent about $25 there on food. Friday I ate lunch at home with the groceries I bought then went to class. Before my song exam, I picked up a drink and cookies for $2. After my exam I went out with Michael and Keaton to Yasubee, which was another $8. Then we went to the arcade where I spent $3. Afterwards we got coffee which was another $3. On the way home I picked up a copy of Famitsu for $4 because Keaton said Smash got a 10/10. Today I traveled to Waseda and ate lunch with Terri at the school cafeteria for maybe $4, then we worked on our skit. I can only account for $50 of out of $80 that has been spent. Where did the other money go? There had to be something else, but I cannot remember for the life of me. I know that I did not go out drinking or partying, did not put any money on my Suica (train card), and didn't owe anyone money. Gah! Give me back my money Tokyo!

UPDATE: I also picked up a magnetic Shogi board from Don Quixote for $10.