I have no idea about this show specifically, but this is exactly why I record everything on my DVR. On Demand is a very unreliable service, and it's not just a Verizon issue. I know people with other services that complain too. You never know if or when a show will be added or removed, so it is best to record it to a DVR and then you know it's there waiting when you're ready to watch.
It appears that none of the popular prime time shows from January 4-6 are ON DEmand! Blue Bloods, CSI New York, Good Wife,etc. Are the Video On Demand folks on vacation? I checked with a neighbor who has Comcast, all these shows are on his On Demand! What's happening????