Gilbert, it sounds like you hit the icon to delete an element on a page, not the file? (The icon to delete a file is identical, but in the file palette, not the main toolbar, and it has a confirmation dialog) We're doing a major design for the next release...
Anyway, it sounds like perhaps you had a major element selected on your page when you hit delete. If you did not save the file, you should be able to close the file tab and tell it not to save your changes, or undo your change. If somehow the changes got saved, I do not believe we have frequent backups (perhaps someone will correct me) The back-end we have in place right now is very basic.