Folder disappears from sidebar

Hi. I have a folder which is stored on my external hard drive. I use it frequently so I wanted to access it quicker by dragging it to the sidebar. When I eject my external hard drive, the folder disappears from the sidebar. I've tried making an alias of the folder and storing that on my mac's hard drive but it still disappears. Does anyone know how I can make it stay there?

Thanks, Thomas

Does it reappear when the drive is mounted?

Does it reappear when the drive is mounted?

Oops. It kept churning, going nowhere...

No it doesn't