Audiogon has three main sections that are somewhat compartmentalized:
1. Marketplace (landing page for this site)
2. Forum
3. Virtual Systems
4. and perhaps less popular sections (Bluebook and Merch)
You must do your search in the respective section, which can be found in the small upside down triangle next to the “A” logo on the top left of the website which drops down the sections previously stated. Interesting enough, you were able to post this thread in the Forum section of the website, which is the same section that you could conduct a search within the forum, which would not be the Maketplace - so perhaps I’m misinterpreting your question.
Example search here.