Well, you can -try- to restore it the old way, but you may end up with an unbootable device that needs a reflash. Or, you can try to mount the images. The optfs is just a EXT2 image; it can be mounted easily on any linux system with a couple commands(mount -o loopback..... for a start) The RootFS is a bit harder; I haven't done it myself. But, your customizations should mostly be in the OptFS, so...