The Disappearing listings is probably a System or IT issue as far as I can tell, Best Buy in the US is notorious for this.
Things are there one day, gone the next, It's probably caused by system or listing updates.

Now, Best Buy Canada does go a step further by deleting "Sold-Out" items pretty fast, my guess is that their CS desk gets swamped with inquiries about replenishment, so deleting the listing resolves that problem.

This is just my theory on the matter from personal observations, I could be way out in left field.

As for the very low quantities, that's a question mark, but I can't help and notice that the same thing occurs with Sunrise and their exclusives.