Died while playing a hardcore mode world, after having built a house. The next day, started a few new hardcore worlds, changing name slightly, but deleted them without dying. Created yet another world, with the same name as the first, and discovered the house I had built in the first world, close to the spawn location. World was not identical, as it had a different spawn point, but seemed to be very similar.

I'm not sure if this is a bug, or intentional, but it does differ from the documented behaviour.