Click on your name in the login line that appears on most pages, or anywhere your name happens to appear, such as next to messages you've authored. This will provide you a list of your most recent message in the last 30 threads you've participated in.
Unfortunately, I strongly suspect this would only "find" the "Proposed New Topics" version of the topic, which has been deleted after archiving. This locations version would not show. This situation is a part of the reason, outside of the PNT situation, we do not delete the previous location topic after it's copied to a new location.
Adminnemooseus