I have the same problem: my Pre 3 got bricked 4 days ago (once it just didn't turned on the screen).
Now it only advertizes itself on the USB as QHSUSB_DLOAD device, but nothing, not even the USB logo appears for the recovery mode.
It would be awesome to be able to resurrect it, but my biggest concern is (for now) all my data on it. For some stupid reasons I didn't made any backup in the last 3 months, and now I'm really worried.
As I've read there is no 100% way of restoring a Pre3 from this state, I would like to know, is there a way to extract the data from the internal partition? As I have a backup device (thanks my foresight), this would allow me to use my favorite Pre3 with my data, and experiment with the bricked device later.
Btw. given the way it used to get hot, it's possible that it got boiled to the point of total failure (as someone else mentioned too).
Is there a possibility to create a working device from two similar Pre3's with the memory of the bricked device and the other working components of the spare one?