Read on as this tip will discuss just that. One day it's there, the next day it's missing from the system tray. But not to worry..
The icon is probably just hidden. Do the following:
(right-click) Start --> (select) Properties --> (select) Taskbar tab --> (click) Customize --> (scroll to) Safely Remove Hardware and make the behavior Always Show.
Alternatively you can keep the icon to automatically hide by default (and leave your Systray uncluttered). If this does not solve the problem, try running this instead:
Start --> Run.. --> rundll32.exe shell32.dll,Control_RunDLL hotplug.dll
... then choose the device to unplug.
You may even create a shortcut for this so it is easier to unplug a device by clicking on the shortcut and not have to recall what command to run.
