I can explain that :) ... when you don't have any cards of one of the starter set monsters, then the system will give you a card to take its place at level 0... You can let someone play that deck or you can too, but you can't sell that card or add to it. Its not a card you paid for, but a promotional card for being able to play for free. (if of course you would like to do so, but I doubt it readying the post) :P

I'm happy to see you've done well on the cards when you've sold them, and while I can see your frustrated, you are always welcome to contact me and I'll help you to comeback again if you want to see if the 3rd time's a charm ;)