Hi,
I was playing an arena game as Rogue/Shaman. I played a 4 drop and transformed it into Deathbringer Saurfang with the location, Muck Pools. When my opponent killed it with a Eulogizer activation + Water Elemental attack to finish it off, Saurfang returned to my hand via it’s deathrattle, but remained unplayable the whole game (many turns). It was not highlighted with a green border, and clicking on it and trying to play it would not work. I was at 29 life when it went to hand, so it had nothing to do with affording the cost.
Thank you.