Lin, up on the left, there are some small icons just below where it says All Things Plants. First is a house, then an envelope, and so on. The 5th one will be for the messages that you have responded to at some point. If you never replied at all to the message that you are looking for, it won't be in there. If that is the case, click on the person looking icon just to the left of that one, which will take you to your profile page. You will be able to find the threads that you started. Just above your picture, is says Actions. Under that it will say View posts made by linjarvis. Maybe that will help?
