just a word of warning, or so....
i managed to destroy all my recordings of recent lahti noizu happening by accidentally removing the power adapter cable before shutting down my zoom H4N properly, so now there are unreadable wavs on the card....
apparently it never finalized the session and it is total crapp now
painful lesson learned:
- keep batteries in it anyway
- always shut down properly
Are the WAV files still there ? Do they have size or just displayed as 0 KB entries ?
If there with filesize, try opened them in a DAW as RAW. I guess you know the bit / sample rate of the recordings. Maybe it's just the header of the files that is corrupted, not other data.
Usually the recording is physically there on the card, but because it was suddenly disconnected it doesn't get a chance to finalise the file, so the computer can't see it
I've managed to recover stereo wavs when this happened tho if you are using 4 inputs I am not sure, one time i recovered those but the audio was kind of interleaved together in some unusably messed up way. But it's surely somehow possible too tho, this was ages ago and I didn't know what i was doing.
Don't do anything more with the card (avoid recording any more on the same card in case it overwrites the lost data) and it should be possible to copy it as a disk image and use some software or other to extract the lost data.
Something similar happened to me, don't format the SD card or throw away the 0 kb files! I restored all of the files using 'Wondershare Recoverit' - tried a bunch of tools, only this one worked. Let me know if I can further help you out!