Ejected USB drive but Plex is still playing/streaming music?!

I have a MyCloud EX2 Ultra, I have my MP3/FLAC music stored on the USB port on my External HDD so I can stream music from Plex. I was going to do a backup to Backblaze for that drive that has a LOT of music on it. So I went into the MyCloud GUI control panel and ejected the drive so I could do the backup. I verified the control panel said it was ejected. At the time I had forgotten that my wife was streaming music using Plex at the time. Anyways when I went to get the USB drive I notice the drive was still spinning. Whats most interesting was that my wifes music was still streaming even though the control system said it was ejected and showed no drive, When I looked at the available directories using the Web Viewer application the USB drive was no longer showing up. So HOW THE HECK was Plex still able to stream music from an ejected drive??? Please advise. Just want to know for future reference. Now that she is done with music I will stop Plex app on my phone so I can actually physically pull the drive out to back it up on Backblaze. Thanks for any insights and help.