Thanks for the explanation. Wish the airlines didn't do this. Makes the hunt so much more difficult.

update: seems like ITA or a travel agent is able to see the availability as well. 3 of us are booked in D. managed to switch 2 of us to K. last passenger left in D. obsessively checked KVS but both D and K zeroed out. only C available. run a saved search on ITA and it priced it in K class. KVS still said zero. called travel agent (airline closed on weekend) and agent managed to snare K.