When building a wall around a village, I tried to place a boat on the ground, to move a villager so they'd be inside the wall when finished. However, when I placed the boat next to the villager, the boat vanished.
So I made a crafting table and tried to use it but it too vanished. I tested some dirt blocks and they disappeared as well. The only block that behaves normally is the stone bricks I was using to make to wall before I tried to use the boat. After about 5 minutes, the items reappeared in my inventory.
Very bizarre.
Edit: For clarification, it was a single player world.
Was this on a server? Blocks disappearing is a common symptom of some server lag.