Macbook Pro - Not picking up Hard Drive
Based on the fact that another known-good drive did not work, it sounds like questioning the cable is the next logical step. You could confirm what you already know by installing your hard drive in your friend's computer and booting it, thus proving the Partition Table/Master Boot Record/Apple Partition Map are in working order.

It sounds like plenty of other people are having problems with their hard drive cables too. 

You can always buy an enclosure for your drive and attempt to boot from USB, ultimately proving that there is nothing else it could be. It's a tad cheaper than the replacement part.

Good luck.