Argos pull off this sort of thing all the time, for a company of there size and reputation its a disgrace but what can be done. Is there not some kind of ruling that they would have to have at least sold some at that price prior to putting up this out of stock BS.
I once contacted them re. a Canon 60mm macro lens at a ridiculously low price, they just kept saying it wasn't in stock. Guess what price it was when it did get into stock ? Yep back up to full (and I mean dearer than most places) price.