Hi Danny,
That member search feature that used to be available is not currently activated. It was a nice feature that would let someone search by state, tractor model, etc. Muhammad has indicated that it will be coming back sometime in the not too distant future.
What I've done in the past when I've wanted to send a PM to someone, was to do a search by their user name. Of course, that assumes ( /forums/images/graemlins/shocked.gif ) that you know their user name. Just go to the search function, and in the space for Words To Search For type the user name. Then, in the Search Options space, open the drop down window and click on By Display Name. I usually make sure that I search for at least 6 months. Just click on submit, and that should show you the posts of the person you're looking for. Then you can just click on the username and send your PM the regular way.
If you don't know the username, then I do exactly what you do. I try to find a post that I know the person responded to and get through to them through one of the replies.
Hope this helped. /forums/images/graemlins/smile.gif