Can't scan network with no default gateway

Hello,

I have a desktop multihomed between my LAN and IOT networks.  I'm using a Realtek NIC which I've configured with a VLAN virtual adapter.  When I first set this up, the Realtek config utility disabled networking protocols on the Ethernet adapter. The new virtual adapter was "the only one" and Fing Desktop correctly picked it up and did what it does.  After that, I went back and enabled the networking protocols on Ethernet so I could get my untagged network back. I also set a static IP in the virtual adapter and removed the default gateway.  This works fine from Windows perspective... one route out to 0.0.0.0 and another route through the virtual for all the little IOT devices on that subnet.  Life is good.  But, Fing now refuses to recognize the vlan as a scannable interface.  I'm assuming that's because it has no gateway.  Is this correct? If so.. why can't we scan a network with no gateway?

Thanks,

Gary