I've thankfully never had this happen to me, but I have had external hard drives die out to the point where I couldn't access anything on them anymore. One had quite a few of important things, so I ended up buying a program for recovering deleted files on a hard drive, even if it had been completely wiped clean. It didn't get back everything, but it did get back a vast majority of stuff that I thought I would never be able to get back.
Not sure if that's something you'd be able to look into, but it worked for me.