We decided to go adventuring today, about 30 minutes after a voted reset, and Alhoon's Lair was completely empty, save for a skeletal dwarf, an assassin vine and a creeper vine. We checked the entire dungeon, including the last floor and the boss room. There was no loot in any of the corpses or the chests, even though the chests were locked as usual, although they had unusually low DC. We decided to check the Shadow Cave afterwards, and there were no shadow asps in front of the cave, and only a few shadow asps and shadow fiends inside. There was loot in the cave, but it was mostly very low value gems and a few gold pieces.
I don't know if it is an issue with spawns disappearing after a reset, or if it is an issue at all, but putting this here just in case it is relevant.