Never thought of that, but I should have. I was in FOK, I had filed three times over the phone after I was told by CD that my flight plan was in the system (even after having the briefer tell me that it should be). After the fourth time, I was p-o'ed and the controller wasn't too happy that he had to punch one in for me.
Ever since the outsourcing of flight service and the several flight plans "lost" I never use flight service for filing. I always use DUATS and have never "lost" a flight plan since its a direct way of filing.