I LOST A VERY IMPORTANT FILE PLEASE HELP ME!?

To begin, I have a very important literature project for school over the summer, and have been working very hard on it. Yesterday, I was very happy because I was almost finished with it. I knew I would be working on it later, so I saved it a few times (I'm cautious) and shrunk it down so that it sat on the right hand side of my main homescreen menu bar. Same as usual. Well, I went to the Apple store a few hours later to figure out why I had used all my computer's memory. The assistant was very nice and explained I needed a backup hard drive, which is what I expected. While he was searching through my computer, he went to the "Permissions" area and had the permissions checked. Apparently things were all out of whack and this arranged them back in order. When he finished, he turned my computer off. When I realized I had still had my reading report shrunken down, I didn't worry too much because I know for positive it has been saved, today and several times earlier that week. When I got home, I turned my computer back on, and everything was same as normal. I went to Pages to open up my document, and IT IS GONE. I have no idea where it went-I checked in "My Documents" my user files, in spotlight, in finder, in my recent activity-EVERYTHING. Any other documents i've ever made are still there, it's just this one, particular document that is missing. How can I get it back? I don't have enough time to redo the project! PLEASE help me! I don't know anything about "Permissions" or what it does. Please I really need your help! THANK YOU SO MUCH IN ADVANCE FOR ANY ADVICE!!! :D