Hi Nozzer,
_ Dear member of SanDisk Community, welcome. _
You have the antivirus (free): Avast!
The raisins, three devices: the PC, the Mac, and then finally to the UFD.
To recover, the converts in “hidden and system” files, you can see the following articles, in which I attempted this topic:
Luck, and then you tell us, what happened, please.
Regards, Alfred. (Google translated)