Question about gnus behavior

[Bob Fry]

I've had this lingering question about gnus behavior and finally query
here for the answer.

I was visiting the rec.aviation.homebuilt newsgroup and killed a
thread with subject "Falcon Gauges". That was the end of unread
messages in the group so I exited.  Then I decided, oh, I did want to
read that thread; so revisited the group.  Since there were no unread
messages I typed 100 for the number of messages to retrieve.  But that
particular thread did not appear.  Why?  I cannot figure out how to
see it again in gnus.

I use xemacs 21.4.21, gnus 1.91.
-- 
We are ensnared by the wisdom of the serpent; we are set free by the
foolishness of God.
 ~ Saint Augustine