Was this a company-supplied work computer or something? If that were the case, its possible that it could have had some security software installed that would enable them to lock or wipe the drive in the event of the system getting stolen, for example, in an effort to prevent company data from falling into the wrong hands.
If it's your own home system without special work-supplied security software installed, that seems pretty unlikely though. In what way is the drive no longer detected? And is it the boot drive, or some secondary data drive in the system?