I had the opposite teacher (also 7th grade), who lost my essay, claimed I didn't do it, and gave me a zero. I still had the doc file, so printed it off again and re-handed it in. But by then it was "past the late turn in date so still worth zero."

Oh, and it was past the late turn in date because she took a month to grade them, so I had no idea she had lost mine until past her arbitrary deadline.

From this experience I learned about covering your ass in communications with authorities, which I don't think was what I was supposed to learn from the essay but it sure worked.