Is it under warranty still?
Your best bet, is to talk to SanDisk...since no Rockbox code ever actually touched the device, you would not have voided the warranty. It is rather a shame that such a length of time has passed, seeing the log of the installation and error logs from your machine may have helped, but that data has almost certainly been blown away by now. I rather suspect the only interesting logs would be from the host machine, all Rockbox Utility is likely to show is a "successful installation" - to the wrong disc altogether - but at least then there would be some clear evidence that Rockbox Utility never touched the device and didn't cause this issue.
The behaviour suggests the flash just...died.
Anyhoo...almost certainly too late now, so...yeah.
Talk to SanDisk, if you're under warranty still...great, if not, I'm really sorry but that is the limit of support that can be offered.
No one here is sitting on a recovery procedure for this device and keeping it to themselves, no one can give you that information because we simply just don't know it...we're just as in the dark as you are. You asked in the other thread how the AMS recovery was found, and, as far as I know it involved the complete destruction of at least one of each of the devices in question and following the traces on the board. There is no guarantee that the Clip Zip even has this "feature" (I am positive that it isn't deliberate) either.
[Saint]