Beautiful flight! I would not have entered that cave either. Surely would have been a switch to atti mode. You maybe would have had to climb up there after all
Not flying into the cave probably saved your Spark and you a big hike to get it. Once inside the cave your drone probably would have gone to ATTI mode (no GPS signal in caves) and if there was any wind down there your drone might have been into a cave wall before you knew it.