You may want to explain a bit further about how is the drive not recognized, is it in Windows* or in BIOS?
In case the data is not a concern it may possible to run a low level format or secure erase on the drive. Otherwise, you may first check with a professional data recovery service as others have done here.
Not found in any BIOS.
Not found in Windows XP / 7 / 8.
Not found via a sata-usb adapter.
No delay when I connected it to my pc via the hot swappable sata2 or sata3 channels.
I've tested this drive in three or four ways:
a Asus 1101HA with sata in ATA compatible mode;
a pc Pentium-4 with sata2 in ATA compatible mode;
a Sony notebook with sata2 in AHCI mode;
a pc i7-3770k with sata2 and sata3 in AHCI mode (AsRock Z77 Professional).
It wasn't found by all them.