There's a spring under there, or at least there should be. The steering wheel pushes down on the spring, which holds the bearing in place. If everything is there, the steering wheel should not be able to get that far down, or the outer tube that far up.
It also seems to me that the tube is normally bigger than the opening in the bottom of the wheel. If the tube somehow worked its way in there, it would be a tight fit.
Here's a thought - if it got so far that the steel hub or the steel spokes rubbed on the top of the tube, the tube may have gotten flared. As it gradually became flared, it wore clearance for the flare inside the wheel, and now the end of the tube is bigger than the hole it needs to come out of. Reaching? Maybe. BW