Currently installed version 10.0.4 build-2249910. Host has 3 monitors and is running Windows 8.1 x64.
This issue has been a problem in past builds too.
Normally running Windows 8 guest on 2 of the 3 monitors under full screen mode. At times I need to view items on the host, so I will minimize Workstation.
Majority of the time, Workstation disappears from the taskbar, so it appears Workstation is no longer running. However, if I ALT-TAB to view windows of apps running, I can see Workstation and select it to get it back running.
This can be annoying at times as I've sometimes relaunched Workstation when I didn't need to.
Lance