Detecting broken threads

Hello and happy Friday Mutt users!

In my muttrc, I have this folder-hook to create a mailbox-specific
macro:

    folder-hook '=lang' 'macro index,pager g<Return> "<tag-pattern>~N !(=s ANN)<enter><tag-prefix-cond><enter-command> unset resolve<enter><tag-prefix><clear-flag>N<tag-prefix><delete-message><untag-pattern>.<enter><enter-command> set resolve<enter><end-cond>" "delete uninteresting messages"'

It lets me delete any new messages I receive under the 'lang' mailbox
that don't have "ANN" in the subject.

I'm really happy with the macro as is. But sometimes, I also delete new
threads manually that I don't really want to store. Subsequently, I also
want to delete any new messages I get that are replies to those threads
I've previously deleted.

So I'm wondering if there's a way I can detect those messages that are
now part of a 'broken thread'. I _think_ I would need to use the
"In-Reply-To"/"References" header in some way to check if there's an
empty match for the Message-ID that it references, but that sounds
a little too complicated.

Is there an easier way?
-- 
	Akshay