If there is no court case, then they are lying to you, which is a big FDCPA violation, in which you can sue them...
Oh by the way, a Debt Validation letter is not a court document, nor should it be sent to the courts. In that case, you would file a Motion for Discovery.
It seems to me that they have no case at all, and I would definitely sue them. FDCPA violations carry with it $1000 (for you) and possible attorney fees and court costs.
And where does Colorado fit into the picture? If they are going to sue you, they need to do it in your County. I'd say it is in your best interest to go to court on this one.