Diagnosing Unrecognized Hard drives I have a macbook pro 13 late 2011. My setup: i have a HDD in the main bay for my files, and a SSD in the optibay with the OS on. The other day i received the message randomly out of the blue which states along the lines of "External drive was unsafely removed" (this was concerning the main bay drive). Ever since i havent been able to see my file drive. 

I have tried removing the drive and reseating with along with the SATA cable to the logic board. I have also tried the HDD on a different machine and the same mac in a enclosure, both didnt recognize the drive. I have also tried perfectly good tested drives in the main bay and they weren't recognized either.

Because my other drive in the optibay is working, im thinking the logic board is ok, but potentially have a dodgy cable and HDD in the main bay?

Can anyone help me narrow down the issue? Or is the next step to try replace the sata hd cable to the logic board, and try a different hard drive.

Thanks for your time.
You said that the drive doesn't work with other Macs or in an external enclosure, so the problem is unlikely to be a dodgy cable on your MacBook Pro. If the drive doesn't work with any computer, it's most likely dead. 

At lot of OEM drives have 3-year warranties from the drive manufacturer. Your drive may still be under warranty so I would contact the company and do a warranty claim.

Also, definitely get a known working drive and see if it works with your MBPro.