Hi
to remove a page from sindice you simply have to ping it again making sure the page returns 404 or similar.
That's the theory. The practice is that these days the sindice pipeline is stuck or stuttering at best. Reason for this is in the shift of focus of the team behind it and a transition to .. either a new team or a end of life (still to be understood).
I sincerely apologize for these issues and for the lack of clarity from the outside - the situation has been unclear internally as well but hopefully to be clarified soon.
Gio