If my opponent plays Authority of Christ and discards all of my blocking EC's, the hero is still in battle and is susceptible to CM, Writ, or several other things that can stop the rescue. I don't see why it would be different (i.e. why the EC wouldn't still be in battle) after the only hero is removed from battle. I have often used Grapes to get an additional rescue after my opponent discards my hero via CM.
So yes, the rescuer can play Grapes/AotL, but Moses is still captured.