You've not provide enough information for anyone to really search for it. Hopefully, someone will remember the thread and is subscribed to it.
Note: Subscribing to a thread that you are particularly interested in is a good way to keep up with it. Buy subscribing, you get a link to the thread on your My Forums page. That page will tell you if a new post as been made to the thread. You can even have an email send to you to alert you to new posts. But that doesn't help you with this thread.
If the thread is more than a year old, the search engine will not be to find any part of the thread more than 365 days old. If the last post was more than 365 days old, the forum's engine will not be able to find it at all. Sadly, on the evening of April 29, 2013, the forum quit properly archiving posts. That continues today.
For those that don't know, when a post becomes 1 year old and the thread it is in has been inactive for a year, the thread is locked and it is moved from the active database to an archive. That archive is suppose to be completely searchable, but we are now looking at 22 months of "missing" posts.
They are not really missing, but the forum's search engine will not find them, which makes them inaccessible using the forum's software.
If you are good with Google searches, you can still find them.
For your thread, if you have a key phrase or word from the thread, you can use Google's search site syntax to find the thread. For example, if one does a Google search for
site:RV.Net "Quite a while ago"
the result pages would have links to all the threads that contain the exact phrase "Quite a while ago" (The search will not be case sensitive so it will also find "quite a while ago"
Good luck.
If you quote this post, the site:RV.Net "Quite a while ago" will become site:RV.Net "Quite a while ago"
Tom