How do I mount ejected external USB flash storage? Suppose that we connect our flash USB drive to a MacBook, then eject this storage from Finder sidebar. Now I want to remount this storage without unplugging and replugging it into the computer, but the disk is no longer listed with diskutil list command.
The problem you describe was initially the intention for me to write an app that allows you to manage your drives from the menu bar. It is called Mountain and you can get it here.

Hope you enjoy it!!

UPDATE: The only way to re-mount ejected external USB flash drives is to unload and load the USB mass storage kernel extension:

kextunload /System/Library/Extensions/IOUSBMassStorageClass.kext


Followed by:

kextload /System/Library/Extensions/IOUSBMassStorageClass.kext


Be aware that this will re-mount ALL external USB drives..