If a series of still images all show some part of the ball was in then you have no proof that the ball ever went out.
The still image they chose was the one where the least amount of the ball was still in.
Could it have been completely out at some point between frames? Maybe, but if you can't find any proof that the ball was ever out then you have to assume it was still in.
Here's the one they were showing on TV, the lighter part of the ball is the bit that is still "in".
If a series of still images all show some part of the ball was in then you have no proof that the ball ever went out.
The still image they chose was the one where the least amount of the ball was still in.
Could it have been completely out at some point between frames? Maybe, but if you can't find any proof that the ball was ever out then you have to assume it was still in.
Here's the one they were showing on TV, the lighter part of the ball is the bit that is still "in".