OK, just to clear up any confusion: yes there was a scene planned where the probe droid would tangle with a snow creature (scripted to occur between the Han/Leia corridor spat scene, and the scene with Luke in the ice cave), but so far as I'm aware it was axed before anything final was filmed.
16 EXT ICE PLAIN OF HOTH - DAY 16
Track with the sinister, probe robot as it moves across
the vast frozen wilderness. One of its extended sensors
detects something and the robot stops, turns and heads
off in another direction, at high speed.
17 EXT MOUND OF SNOW - ICE PLAIN - HOTH - DAY 17
The robot stops before a large mound of snow about
twenty feet long and six feet high. It circles the
mound, then shoots a thin laser bolt at the snow drift.
18 CLOSE-UP MOUND OF SNOW 18
The mound shakes a little bit and two large eyes appear
at one end, staring directly at the robot. A primeval
BELLOW issues forth from the mound.
19 EXT MOUND OF SNOW - ICE PLAIN - HOTH - DAY 19
The robot backs off a few feet, then blasts the mound
with a heavy laser bolt that disintegrates the snow-
covered creature in a cloud of smoke and flame.
20 EXT ICE PLAIN - HOTH - DAY 20
The evil robot moves off toward the horizon.
As you can see the script doesn't specifically identify it as the same "ice creature" that would later be called a wampa, only describing a pair of eyes under a snow drift. Indeed some materials refer to it as a "snow squirrel".
The creature for that scene was planned to be realised with a stop motion puppet, but they cut it for what I am presuming were time and money reasons; Tippett already had plenty on his plate at that point, and the production was already running over budget. However,
some elements were completed before the cut (the squiggly line is meant to represent the "snow squirrel".) So I'm reasonably sure the thing was never designed or built, let alone animated.
Yes they did try and film the wampa invasion scenes despite the fact the suit was a nightmare to use on location. Several shots were completed, but they were just as unsatisfactory as the location stuff and were ultimately deleted, with a simple but effective hand puppet and some sneaky editing replacing most shots of the original suit.
When it came to the Marvel comic adaptation, they didn't include the probot/snow monster encounter, but they did keep the wampa invasion subplot and included a deleted scene of it attacking one of the rebel's perimeter outposts right before Han & Chewie go out after it (which I'm also reasonably sure was never filmed.)
The novelization seems to be where the conflation of "snow squirrel" and "wampa" occurs.
"The mound shook again, with a roar that nearly destroyed the probe droid’s auditory sensors. It zoomed back several meters, widening the space between it and the creature. The droid had never before encountered a Wampa Ice Creature; its computers advised that the beast be dealt with expeditiously."
