none said:

^ http://www.starwarz.com/tbone/index.php?categoryid=10&p2_articleid=412

Explanation and pics at bottom. Here's some of the info:

The only thing that really makes me believe this scene was actually shot (besides the look on Mark Hamill's face) is the following quote from Jon Knoles in the Star Wars Insider, Issue #33 (page 59) talking about the game, Shadows of the Empire for Nintendo 64:

"We knew, for instance, of the scene where a wampa actually broke through into Echo Base and mauled a tauntaun (and possibly some Rebel troops) and a scene where Luke actually took over an auto-laser cannon and blasts a wampa or two. The wampa filmed in this shot looked absolutely hilarious with a big fluffy face and metallic round eyeballs. We saw the picture in a Kodak shoebox Photo CD that Lucasfilm Ltd. provided us with some time ago."

The picture of Luke using the cannon is just a publicity photo. The Wampa attack happened before Luke was even rescued, just before Han goes out to look for him.