User Account component removed, but user stays

I'm hoping someone could help me out. I've ran in to a problem when I
have added user account component with user name/password combination,
but then had it removed form the .SLX. However now, when I login as
administrator and attempt to create same user from control panel, I get
an error message that user already exists and that's in new build with
component removed!!! However, there's no user with that name listed in
user manager or anywhere in the configuration. Is it a glitch? How can
I remove this "ghost" user completely from the system?

Please help.

Thank you!