Would it be worth having a spammed, duplicate and expired section.
Also where you have the spammed and expired buttons have a duplicate one too.
Automatically move all expired, spammed, and duplicate threads into this new section.
Then when a thread is tagged as such it is still viewable and maybe a comment can be added to show why it was tagged as in duplcate or expired.
This would do away with the 'where has my thread gone' posts and also give the OP a reason as to why it was tagged and moved.