Music Disc 11 in Survival Multiplayer.

I have gotten the music disc "11" which is said to be only available in creative in survival multiplayer. I got a creeper to low health with an arrow, a skeleton shot it and it did not die. It was about to explode so i punched it and it died and dropped the music disc "11". There are NO server mods or plug-ins, it is a server for me and one friend. He was not online or in game, and commands are NOT enabled, even for him (the owner of the server).