If you right click on the toolbar area, it should have a list of available toolbars, choose the menu bar.
It's possibly you hit F11, which changes your screen format to full screen and removes your menu bar... click it again and see if that fixes it.
If you can't figure out how to get it back, try hitting alt then f. Alt should pull your menu bar up whether it's showing or not, and the letter f (not one of the f__ keys) will select the File menu. This will let you access it, even if you can't see it all the time.
Good luck!