Macbook sleeping on low battery causes my USB drive unreadable

Hi everyone.

So I was copying a few gigs of files from my MBPr to one of my USB 2.0 flash drive this morning. Due to the relatively long time it required of the process I just left my computer there, not to expect that computer drained battery so fast as to turn to sleep within an hour. When later I woke up my MBPr, I found two messages concerning my USB drive:

1. A warning with roughly the same meaning that "the file is unable to be written to the selected directory."

2. "The disk you inserted was not readable by this computer," with three options: "initialize", "ignore", and "eject'.

This reminded me immediately of exactly the same problem happened a few years ago that I lost my data on another USB drive permanently, though I didn't pay much attention to it that time and thought it only as virus infection. I guess the problem might well be caused by the low battery auto-sleep, which shut down the power supply for USB port, equivalent to unplugging the drive while it was transferring data. I searched for some solutions about recovering original files on USB drive yet none of them worked because the drive just can't be recognized either on a Mac or a PC (on windows it said the drive is in Raw format).

Can someone help me to recover my files safely? They are kind of important so reformatting is the last option I would try. Also, is there a way to send this issue to Apple after my warranty expired? I think this should be treated as a bug of auto-sleep. The read/write process should be suspended before the power is off to avoid any data corruption.