Removing a Record From an Index

How do you remove a record from an index? When a record enters a state
of “inactive”, we want to remove the record from the index. I have tried
calling self.ferret_destroy but this destroys the entire index on the
Mongrel on which self.ferret_destroy is called (this Mongrel returns 0
records while the other 3 Mongrels continue to return records). Is there
another method I should be calling?

I am using AAF 0.4.3, the plugin, which includes the acts_as_ferret :if
=> Proc.new { … } option.