Got a Sacred Rubber Sapling (615:1) in a treasure bag.
I planted it.
The room I planted it in became an invisible maze that I might not survive getting myself out of, because it won't let me jump up, it won't let me go up the ramp, every time I break a block, the next chunk of wood appears. :P
I logged out, and logged back in and the logs became visible. :-) Repairing the room is going to take time.