Here is the link to your gallery with your photos - https://www.bikeforums.net/g/album/18036484

You have a threadless stem, the stem cap, as well as the 2 bolts for the stem are required. I would not recommend you ride the bike without top stem cap since it helps keep the headset/fork from developing play. It wasn't very secure previously if the star nut fell when you removed the bolt.

I'd slide the fork off the frame (may have to unhook your brake) and shake it upside down. Steerer tubes are also hollow so you may be able to access it from underneath.