The "Twiggy" drive actually made it into fairly late prototypes. If you look carefully at some of the photos in 1984 Newsweek ad you'll notice that the floppy slot seems unusually long. (Look particularly at row 2, images 1 and 2, and row three, first image.)

There's also some prototype images over on Applefritter, which point out the long floppy slot.

That said, I suspect the OP would of been a lot more excited if he'd found a 128k with a Twiggy drive. Is it possible that some early Apple disk labels called the 3 1/2 disk "Fileware" as well? I have no idea. (The 400/800k drives *are* sort of a bastard hybrid of Twiggy technology and Sony's drive mechanism so you could make a case for it being "Fileware 2.0)