Matthew - one extra point. You can recover your work , but its hard:
You would first have to import the QVF into a QLik Sense Server , remove the SECTION ACCESS via the load editor, and then do a successfull refresh on the server so that the security is flushed out ... then you could export the unsecured QVF out of the server and reopen on the desktop.
Its convoluted i know so lesson is ... always back up your QVF before applying Section Access. whether you have a server or not.