Hey dude, don’t apologise, can be frustrating when something small like that happens. I suspect that your composition window has been switched to maximize (like in all windows windows (?:-) and Mac windows, at the top right hand corner of the window box are 3 tiny icons, one usually minimizes the screen, one toggles between maximized (full screen) or floating windows box, and the final one closes the window all together (they are in that order left to right in windows). Simply look over to the top right hand corner of the screen (in line with the menu bar) and click on the middle tiny icon (represented by two overlapping pages when in full screen mode), things should go back to normal. 🙂
When in full screen mode, if you have a mouse with a scroll wheel, you can use it to zoom in and out of your image and holding down the space bar while left clicking allows you to move around the image window (where normally you’d have scroll bars, …this is a quicker navigating method).
Hope that helps!
andrew
🙂