Uhh, you got a big problem.
First: Do you have the little book in the CD box wich you get when you purchase the original CD. On the last page there is a CD key. Try to take a look for it!
Second: Maybe you can find the CD key somwhere in the Instalation like it has "Elbe", "Furie" and Collectors Edition. Try to search.
Try to find some proof, take a picture of a recept, of a CD box, CD or some other things...
If you found something send it to VSTEP.
The last what you can do is to go in the shop where did you bought it and ask them if they do remember you, if they do, take them as a witness.
Try to found the key in the house...
GOD LUCK!
Welcome to the forum!! And if you do find the losted key the first thing if you find it REGISTER IT ON THESE FORUM in you profile, so you can always had it, and play the multiplayer.
Kind Regards.
Capt. Mitch