Remove duplicated user from TFS2012

Hi,

We have TFS 2012 in our organization and 2 different forests with full trust.

Both forests holds same logon account (domain-A\alex + domain-B\alex) while display name is different.

While user was working on TFS with domain-A\alex account everything went smooth.

Now, on one of the servers he had a workspace with some checked out files, and the server was deleted with no option of recovery.

I want to "undo" his work via power tools (or some other way) but every time I try I get an error indicates that TFS holds 2 users with same logon name and different display name.

I tried also to delete this user from AD (either one, there is not just "Alex" account with duplicated logon name) but the error still exists. I still see the user in TFS admin portal although he doesn't exists anymore and I cannot delete it (sync to AD is working and healthy)

Any ideas?

Thanks