Is the disk visible in BIOS Setup? DU should show all disks, no matter the partitioning/contents. Maybe your SSD has gone faulty and that's what caused the OpenCore error rather than the other way round.
I take it that your E6430 is fitted with 2 disks: one in the usual SATA slot and the other in the modular bay, right? If so, maybe you can try to swap them around to check things out. Then, it'll depend on which one carried the bootstrap of course. If I remember correctly, disks fitted into the modular bay required a patch of some sort to be seen in OS X/macOS.