Gill,

To properly lift an Elise on a 4-point lift, you have to remove the undertray to expose the lift points. The easiest way to change tires on it, I've found, is just to jack up one side at a time with the center jack-point, which is exposed and doesn't require removal of undertray.

They lifted the car apparently without removing the undertray, and probably used the center jack points as the rear lift points. So it was precariously balanced... When they removed the front wheel, the weight balance of the car was thrown off, and the whole thing fell backwards off the lift.