If this happens, simply click little arrow pointing down next to EDIT and then select HISTORY, there you see all changes to page and you can also undo them
example :
(cur| prev) [friendly button] [date] [ip address] (wall) . . (empty) (-number) . . (Removing all content from page) (undo)
if you click undo, it will undo all changes (in this case, undo removing all content from page.
Hope it helps those who rage when they find out their text was removed..