So I had been doing this ant dungeon alone for the past three days, when i'm finally able to finish it, as i'm butchering the corpses of the ants and loading the queen into a cart I get kicked out of the dungeon.
I lost my horse, ant queen corpse, cart and some minor loot in there, thankfully I had put the heart container and crown in my inventory.
There is no warning that you are going to get kicked out of the dungeon once you kill the queen, which made me assume that maybe the dungeon would despawn only after players have left it. I honestly feel robbed of hard work by a game mechanic...