Is it possible to erase sensitive data from a dead Retina MBP SSD?
Fire. Unfortunately that would seem to be at odds with Amazon's return policy.

If Disk Utility can't see the drive, it's unlikely you'll be able to access it to overwrite anything (and overwriting on SSDs can be tricky in any event). Additionally, because the drive in the rMBP is a proprietary form factor, it's difficult to take it out and try to access it from another computer (which might not help any way). There may be adapters made in the future, but I'm not aware of any for sale at the moment.

The best preventative measure for this would be to employ some form of whole drive encryption, like Apple's FileVault. That way even if someone is able to read the data off the drive, it won't be useable unless they have your encryption password.