While I don't know how much help I will be or if I will give you your answer that you're looking for...well, what mission is it? I can see what I can do!!
Is it the Mission that Xion is with you? The one that is fairly early in the game? Because if it is the emblem that is over the shop, I think I have an answer. But I'm not sure. Please tell me, and I'll try and help you!
it's the 1 with xion the mission is a pain cuz ur halfway there she comes and you fall missing it