Others have asked about this issue but had intermittent access to their HD, therefore their results did not apply to this situation. I have tried reseating the HD to no effect. I also tried booting from the Internal HD to no effect. Next step get a connector cable and move the data to a different HD, or send in for HD recovery? Any suggestions?
Due to the unfortunate possibility that the drive has failed, i would first attempt to recover the data by connecting the drive to a desktop computer, or a USB dock and see if you can recover the data yourself. If it works immediately backup your data so you no longer have to worry about it. Once your data is backed up look up the HDD manufacturers recommended testing method (seagate uses seatools). If it passes all the test then the port on the motherboard of your notebook has gone bad and you want to look at repair options.
If it does not pull up in another or on a USB dock then the drive is probably bad and you want to consult with the HDD Manufacturer about recovery options.
Some say you can freeze a HDD to recover it but be extremely careful with freezing the drive because condensation may render it unrecoverable at all.
Best of luck!