Thanks Dan!
The three photos I have of the interior of the cave don't show one installed. But I don't see any wires capped off either. I'll check it out when I'm at the boat next time.
If the prior owners pulled it out, I'm surprised it wasn't picked up during the survey I had done. I've installed a 12 v unit on my prior boat and know it's an easy and important install. If I need to install I think I'd rather locate the CO detector just inside the V-Berth next to the port speaker location rather than in the cave.