well there are a few ways that could have happened...
1- a cd key generator could have randomly generated your cdkey and he/she just happened to get it...
2- someone came to your house and stole it
3- you are being possesed by a person and he has made u say your cdkey in your head for the soul reason of getting a d2 cdkey.....
4- your server is a bad server
5- bnet is gay like that
6- dont no what else to tell ya...... 3 was a joke

thats all i can think of sry