Xbox 360
Monsters University
I was playing around and doing the quests in Frat Row. There's a bunch of quests in there that require you to buy items from the Toy Store. When you accept the quest, the item unlocks in the Toy Store. I got a quest to buy JOX House, but I didn't have enough money. Grinding for money in Frat Row is tough, so I left the area. When I left the area, the quest was removed from my Quest Log. When I had enough money, I went back in and bought JOX House. However, the quest giver still had the quest and I could accept it, but not complete it - leaving me stuck with an unfinished quest.
TL;DR - In Frat Row, make sure you have the quest to buy a thing before buying the thing. Either that, or don't leave Frat Row until you're 100% done with it.