Thanks to Steve Witt, of the LEGO Community Team, we now have an explanation as to why this set popped up unexpectedly, and why it disappeared just as quickly:
"The Ultimate Space Battle was only ever intended to be a 4th quarter exclusive for Target, and it sold very very well (hence why its gone already).
Since its retirement there has been a footnote at the bottom of the Ultimate Space Battle
page at the LEGO shop@home website explaining "We’re sorry, this Collection is no longer available. Please see our new, exclusive replacement Collection: #K7283 V-wing Space Battle Collection." Sadly LEGO did not provide a link to K7283, nor did appear on the website.
Yesterday reader Trip O'Neal wrote in to point out that the V-wing Space Battle Collection
was up for $44.97 (USA & Canada only), and Steve Witt has added:
"The V-wing was added into a new collection (K7283) and placed up on Shop@Home. Whether this was done as a replacement for the USB or just as a holiday collection I’m not certain.
So, for now there is another new LEGO set to add to your collection - assuming you feel the need to pick up yet more Vulture Droids and yellow Jedi Starfighters.