Magic Missile Was A Dud
I cast Magic Missile, targeting a 4/2 Wildwood Patrol creature and a 1/1 Ilysian Caryatid creature. In response, my opponent cast Fire Prophecy, targeting my 5/3 Orcus creature. I respond by activating the ability of my Skullport Merchant, sacrificing my Orcus. When the stack resolved the following happened: I drew a card, my opponent was able to place a card on the bottom of their library and draw a card but Fire Prophecy had no target to deal damage to and so fizzled out, Magic Missile sat on the stack and then resolved without dealing any damage to any of the selected targets. Nothing on the battlefield, nor any of the cast spells, grant indestructible or hexproof.