Did not drop it or cause any trama to the device. It was working fine and then all of a sudden, the device is not recognized. I tried it in another computer too. It seems totally dead. Any way to fix?
It sounds like the NAND memory and/or the controller on the USB drive has stopped working. This is a sad situation for everyone involved.
Your best bet is to contact the drive's manufacturer. They might have some troubleshooting ideas that you can try.
However, usually in situations like this, the data on the drive will be very difficult if not impossible to recover. Sorry. I've had this happen to me, too. It's no fun.
NAND flash chips are somewhat unreliable in general. In SSDs manufacturers compensate for this by installing several chips and keeping the usable capacity lower than the real capacity. This way, when a chip starts to fail, the controller can move blocks elsewhere. However, in small devices like USB dongles, this is usually not done, and sometimes not even possible space-wise. Thus, USB dongles fail. Use them to move stuff around, but never keep the only copy on any one device, and especially not just on USB dongle.