Can a third party sue you if the original creditor has no information on you?

I am trying to clean up my credit. I have an old credit card debt from capitol one, it started as a 50 dollar card and after interest it is up to $2000. But I have contacted capital one and they have no information on me or my social security number. I have disputed the debt on my credit report and heard nothing yet. But in the meantime I get a summons that a lawyer is suing me on behalf of capital one(plantiff) for the whole amount. Can they do that and how do I know they are working on behalf of capital one if they don't have my account?