I'm from the UK, and I'm sure I've seen it - from the description of the bts footage of the fall of the first AT-AT, I'm sure I've seen it. Years ago while in college, I gave a copy of the SPFX doc (which I hadn't watched in ages) to a mate who was studying animatiion - specifically so he could see that piece of footage, and he reported back that the tape I gave him didn't have it. I watched it again to make sure, as I knew for certain that I had seen it in a 'making of' for Empire, and he was right - it wasn't there.

I've been asking people for years if they remember it, and some of them remember it, but none of them can find it in their collections.