Just did the same thing!! I am working on a table runner... Thought I knew how to do it and was not paying attention to the directions, came upon a snag - I needed to rip off (gently, of course) one triangle - only one! - set the project aside for supper (darn that need!) and when I went back to it I forgot about the row already sewn together and went on to the next one... one whole row has been left out - THANKFULLY no one will ever know ;)