I am in the same boat.
I have a wordpress.com blog/account.
I have a www.remarpro.com account with a self-hosted blog which no longer exists that shows up in the global dashboard at wordpress.com because I needed to get the API for WP Stats & Akismet plugins.
I now want to map the domain of my wordpress.com blog to the domain that the self-hosted blog was on. Can’t do it. I want to delete the self-hosted blog off the drop-down at wordpress.com. How?