Look at it this way. What if they locked it out before you joined. You probably would have never joined.
Long story short - We all experience loss of our work, from both server crashes and single player. If you want to play without minges and server crashes you have two options. Make your own server and lock it, or play single player. Multiplayer servers are there for everyone to enjoy - for new players to come join the community, and old players to continue enriching the community.