There is barely anything known about this lost pilot, and there are no images nor videos about it whatsoever, and this has yet to be explained more.
However, this pilot actually exists, as confirmed by creator Joe Brumm. Unlike the 2016/2017 pilot a lot of us know, this pilot has a completely different plot, as it apparently shows Bandit (who is voiced by a different actor) pushing Bluey on a swing, before pushing it to the point where she does a 360 around it.
The pilot was never aired nor revealed, not even showing a single image because according to Brumm, the act that Bandit did was "too risky", and "something you wouldn't want your kids to see", and it apparently had copyrighted music (which is also not confirmed).
As stated above, not much is known about it, and it's unconfirmed who voices the characters and how the animation goes, and if it just shows Bandit pushing Bluey on a swing.