Bukkit Game Corrupted All Work Lost

Hi, so my friend was making a small bukkit game on his computer for a giant parkour map andd he left the server on overnight after saving the game with /save-all.
The next morning he came back to the server and entered the game and the map was totally different. It was flatgrass, like before, and had flowers and tallgrass like before, but it had trees which it did not have before and a strange giant ocean/lake thing with a small island in the middle of it.

He has Windows 7 so I tried loading a previous save in the properties of the world file but there were no previous saves. I was going to tell him to shut down the console without typing /stop or saving but he had already done so before calling me to help.
Thanks!

 

Have you got any screenshots of this? Also, could you report which version of CraftBukkit you are using; thanks

 

And that's why you use back-ups

 

Thanks for answering, it turns out that it was only the spawn point that changed and he was teleported to a far away part of the world from his creation (is what he said).
He found his maze map and used a plugin to set the spawn back to where it should be

I told him it was probably his player.dat file that was corrupted, and that he should back the whole server up.