If you are logging into your server and use command line to login as admin, you can use cheat worldsave command to force a world save before turning the server off to make a save at that moment! You should always do this before shutting down a server. If you just shut the server down then you may only have the last save and the server really only saves every 15 to 30 min or what ever you have its save and backup intervals set to, may even be every hour or 2! I always login and force world save just to be safe, it saves a lot of head aches and never fails!