Sometimes the Internet is correct!
Had three hard drive failures within a year, one while I was in the middle of saving something! No warning or notification, just stopped. Upon restart, got the dreaded blinking folder with a question mark. Upon searching Google for multiple frequent hard drive failures on a MacBook Pro, the collective wisdom of the Internet said it was a hard drive cable! Hard drive cable? How often does a CABLE fail? In a sealed computer? Well I thought, it was either that or a logic board, so I thought what the heck, I'll give it a shot.
Cable replacement was exactly as directed, got the version which had all the hardware already attached, so I didn't have to go through detaching very small connectors. After installing the new connector, buttoned the computer up, turned it on, and boom desktop was where I left it! Excellent! 6 year old Mac is back in business!
Sometimes a problem which on the surface does not make sense actually is a problem. Need to get multiple opinions on confirming the problem's existence though.