This also happened to me after failing the persuasion check during the Astation feeding cutscene! (I had to reload). Curiously enough, in a different playthrough, it was my PC that ended up dead after Astarion got overzealous with feeding. The game did register the PC as dead this time around, so I brought them back via Talkative Skeleton. I suspect that the second scenario (the PC dying, not Shadowheart) is how this checkpoint failure is *supposed* to go.
