Wow, I would call Mulder and Scully for this one. Burning that much oil, you should have had some visual sign of something. Either from the exhaust or smoking from under the hood.It couldnt have just vanished, had to burn off somewhere. Although, my guess is, with no visial signs, it burned off from the inside. As Joe said, I would check the radiator and see what the color of the coolant appears to be. I can only imagine there was a crack somewhere along the cooling train and it burned off through there. *shrug* No matter though, it still doesnt change the fact that you are in need of a new engine. Now is your opportunity to go with a direct injection. And ya, it is still cheaper than a new car.

The VX sure would have been more handy with an oil press gauge. One of the first things I added to it. Hopefully it will give you a better warning than a Check Engine light will.