Moosetamer,

You can access a specific member's past posts by clicking on their name.  That'll take you to their ID page.  On that page you can elect to look at that member's last ______ posts (# of past posts = your choice).  You may have a lot of searching to do IF that individual has been a member for a long time & has made many posts.

In most cases, I can zero in a given individual's post simply by using the basic "Search" function & using specific words that I can remember from that post.  It certainly helps, too, if I have a sense of about how "old" a post might be so I can feed that info in as close as possible.  

Good luck!     :)

Jimbo