But as this isn't a U3 drive, that isn't much help!
However if the OP can get the VID and PID from the device (as he got the serial number) there is a chance that it can be identified and then offer a way round the problem (if there is one - ithe controller on it may have been programmed so that it is two logical drives) but until the make and model is known there isn't much new advice to offer.