Actually if you just lost the toolbars, and immediately are aware of the
fact, you would not close excel but
open your .*.xlb file with Excel still open to replace what you are
using with what you had when you previously used Excel.(when Excel last opened/closed)
http://www.mvps.org/dmcritchie/excel/toobars.htm#emergency
Once you've closed Excel, you would want to try to find out what you had
done and correct that, if possible, before resorting to renaming your
*.xlb file and having Excel create a new one. All of your toolbar customizations
and your own icons, and menus are stored in that file. You should be
including it in your backups.
http://www.mvps.org/dmcritchie/excel/backup.htm
But from what you describe possibly you are in Full Screen mode
View, click on Full Screen mode to turn on or off