All items and XP lost, spawning in 1 block lower on Y axis when loading in world

Made a small house with an inverted slab floor and decided to log out for the night. (Single player world). Had a horse with golden horse armor on a fence post outside of the house, full diamond armor, iron tools, and an enchanted fishing rod at the time of logging out. Logged back in about 2 days later. Spawned inside of the floor. All EXP (about 15 levels), inventory items, armor pieces, and the horse (along with the lead) were completely gone.