It's kinda not bug, it's just the way how soundcards detection is done. My USB mic on my headset is also not visible, but on same headset, headphones are visible.
Funny thing is if you set that input device as default in windows and set Default device in ST as input, it works just fine.. so it's just not in ST's list.
Any chance this will get fixed/updated? What could be causing the non-showing of some devices? I imagine the mono channel. But unfortunately some mics and audio inputs are mono.
For now another workaround is to use Virtual Audio Cable's "Audio Repeater" application to patch the hidden mono card into a Virtual cable which works in ST. But this requires another program to be open on my PC.