Was that the PvP server (play.minecraft.cc:23456) where you can kill people? Or was it the build server (play.minecraft.cc) where health and Monsters are turned off?
And where was the hotel, near spawn, far away, north south east west?
By the way: If the hotel was very close to the spawn (where all people appear if they have never been to the server before), that's obviously the place where the griefers are most active. Whatever will come of this, you should try to get away from spawn and then chat "/sethome" from time to time to set the point that you can then teleport to with "/home". You can teleport to spawn anytime by chatting "/spawn", so that you and others can trade etc.. If you make your buildings a few thousand blocks away from spawn, they are usually safe from griefers. To see your location, press F3 (while in fullscreen, or you might not see the coordinates). Notch will probably soon remove that feature because it's technically a cheat.