I was testing to see if I could drag individual notes to the favourites panel when I suddenly I realized that the notes were disappearing. It seems that, although I let go the mouse over favourites, I had dragged the notes into another notebook.
Because I was just testing the idea of dragging notes to favourites, I didn't pay any attention to which notes I was dragging, so now I don't know which notes I've moved to where. 
Does anyone know if there is an "undo last action" option? (And/or a way to restore to yesterday's notes files?)
Thanks