Sometimes when in Vanish, players can see me or other mods just floating and other times we are not visible.
The hotbar is the 6 spots that are presented in front of you when playing, Lets say I am holding a gun, and then I go into Vanish.. the gun I was holding is no longer visible to me, but I can still shoot from it. come out of vanish and the gun that I am holding is again visible. I would have thought regardless of my vanish state I should always be able to see what I am holding, and for example if the gun has a flashlight attachment, while in vanish I should be able to use that flashlight to see in the dark. (mentioned below by another example)
The picture above shows a player holding a gun, not in vanish the player can see his gun, then the other picture is the same player but he can no longer see his gun, he is now in vanish.
another example is I have a flashlight attached to my gun while its dark and i'm not in vanish, I then go to INTO vanish mode and the gun and flashlight disappear and I can no longer see where I am going as the flashlight which is attached to the gun is gone. While the gun remains in my HOTBAR its no visible, nor is the light which emits from the flash light.
I hope this gives you more clarity to the situation.