A professional data recovery service may be able to restore lost data.
I don't mean the Geeksquad-type guys in a laptop/cellphone repair shop who'll run a bunch of hit-or-miss "professional" data recovery software. You could run that stuff yourself, and you'll probably get the same "sorry, we only got some of it back" or "sorry, it's all gone forever" results.
I mean the guys in a forensic data shop who'll use lasers and microscopes to read (copy) logic bits directly off the nvflash substrate before running data reconstruction software. A surprisingly inexpensive (largely automated) service, though the chips themselves would be destroyed and need replacement so it's only worthwhile if the data is more valuable to you than the device it's stored on.
If you're serious about recovering data from any machine then the first thing you should do to maximize chances of success is to power the thing off and stop using it. The more it gets used, the more "empty" (deleted but not actually erased) memory cells get overwritten with new data.
