Having gotten a secondary inspection myself because of forgetting to bring a letter from my internship that I was going to, I know what it's like, but if you don't have a suspicious story or one that's easy to track down, it shou;d be fine.

Another post mentions money: they just want you to have enough till you get out and not be a burden. They asked me what my parents occupation was (they were my backers), and I did have documentation as to that (their payslips), not that they cared much.