I seem to remember this scene as a child. A damaged Snowspeeder crashes right into the cockpit of an AT-AT destroying it. I'm not the only one who seems to remember this scene, yet I can't find it in any version of the film I have.

A few examples of others describing these scenes:

I used to watch the network television versions of the films that I recorded onto a VHS, so that is my best guess as to where I saw it if this scene is even real.