Probably unrecoverable.
USB drives are just a cheap memory chip in a case, so no backups, no redundancy and once its gone its gone. They are static sensitive and a single spark can fry enough of the chip to render them usless.
It'll always happen when you least expect it, or need the data the most, which is why you should never rely on them. They are probably more reliable than floppy discs but their very capacity makes folks think they are an alternative to good storage systems.