Assuming it's also not showing in the BIOS when plugged into a system, and since it's not being recognized by the OS(s) you tried, the bad news is it sounds dead. The better news is, it may just be the power sub-system, and the data may still be in the flash memory.
I'd have to say your best bet is to send it off to a professional data recovery place that does flash media. Many (most) offer free evalutation and quotation, you just have to pay the shipping. Most also offer that if in the end they can't get it back, you don't pay.
You can then decide if the recovery fee is worth it, without investing much.