Is this the correct diagnosis for hard drive not being read?

As follows is my diagnosis process. I believe my hard drive ribbon cable has failed but I would appreciate confirmation.

1. Booted laptop and got the question mark folder symbol.
2. Tested drive by copying off its contents onto another computer. Drive was healthy.
3. With the old hard drive connected externally through an enclosure, I booted the laptop off of a USB connection, with no drive inside. This restored full functionality, but is not a desirable solution. Thus, the logic board should be healthy as well.

Is the ribbon cable the only thing that could be broken here, or is it possible that the headers on the logic board are broken/something similar? I still see the front on/off light turn on and off correctly, so one would hope the headers are fine, but I would appreciate any input on other routes of failure.