Question World resets when switching from Bukkit to Vanilla

Hey there!

A while ago I've built a cool castle on my bukkit server and I decided to make the world downloadable. I quickly moved the file & uploaded it over to Mediafire. Not long after I've recieved a message that the world I sent was a regular world with no buildings on it. I found it weird so I downloaded the map myself to find that the Castle was gone. It was basically the same world/location/etc but the building was gone, like I never built it.

I got scared for a while but then I re-downloaded the file on Mediafire and placed it on my server to see that it worked perfectly fine, the castle was there aswell. I instantly moved the file to vanilla in %appdata% - .minecraft - saves and went on game to find the exact same issue, the castle was nowhere to be found.

I've came up with the conclusion that the world works on Craftbukkit but when I transfer it to Vanilla the content inside resets ( As mentioned earlier, same seed and location and everything but without the build )

Any ideas?