KingMax Usb Undetected
Your friend likely pulled the device while it was updating the index without "ejecting" it. We all do it, but it can lead to this often fatal problem. Right clicking on the drive, you'll see an option: "EJECT". This doesn't physically send the drive sailing across the room, it simply should be called:
"Shut Down External Media For Safe Removal".
When not done, this can cause the index to fail, and as a result, when re-inserted it basically shows as a drive with no information. No index, no way to tell what's on it, how much space is available, etc. It will usually recognize that the drive is connected, but won't respond.
To the computer, it a 'Schrodinger's Cat'.
It's both full and empty simultaneously.
Sometimes if you plug it back into the computer that it was in when the failure first occurred, THEN powering the computer on, it MIGHT still have a copy of the index file and MIGHT reload it. Otherwise, there are programs that can recover the data without indexing, but it's a chore to reconstruct the files. Data reconstruction and recovery services can work, but are really expensive. What's the data worth to you is what you need to ask yourself. EJECT your media!! This happens all too often!
(If the item that the media is plugged in to doesn't have an eject feature (such as a music player), shut down the item before removing the media)