Just checked, I don't have the diag board that supports that disk, but I could get it, so it won't be one of those billable 1-2 hours of my time. It can be recovered with the board and a dictionary attack if toshiba won't just unlock it for you.
Note that the disk is NOT encrypted, it is locked. This disk does not have built-in encryption firmware. Did you take the time to test the disk in a different computer? This exercise is pointless if the disk is protected via an easy-to-defeat BIOS lock. You can see if the disk uses add-on encryption software by running a binary editor and attempting to read the first few blocks while disk is in a USB enclosure. If you can read the disk then you have software-based encryption. If you get errors reading the disk, then it is locked. Very different recovery techniques.
Will be unavailable till late afternoon, but I expect others who deal with encryption & diagnostics can help if I am not around. (Just don't run chkdsk /f, this has small potential of causing data damage, and will not fix anything)