First, you are writing of some sort of casual static discharge where the thumbdrive is in the current path. That would be unusual enough unless you slid across a wool carpet and then used the thumbdrive to ground yourself.

But, I expect you would need something on the order of a static generator to make enough current to actually do damage.

Try this: Purchase a very cheap thumbdrive, and try to wreck it via static. You should be reassured by the results.

Peter Wieck
Melrose Park, PA