Well, one nice thing about it being an SDHC card and not an SxS card is that you can throw it into a garden-variety card reader and try a number of recovery utilities. On a SxS card you’re hosed that way, at least in my experience in playing with a few “what if” scenarios.
My guess is that even if a file recovery utility was able to find and recover the files on the card, it will NEVER make sense of the cryptic nature of all the folders, subfolders, and other little files associated with the metadata. That’s because the directory information is gone, and these utilities actually look for orphaned files on the card. So just try to get the MP4’s restored. Then see if you can use Clip Browser to rescue those into a new BPAV folder on your hard drive of a new card. You may lose metadata but recover the footage, which at this point seems like a best case scenario.
Cf