You send it to the person who it belongs to. Then when the want to check if their vote went through properly, they can look up the vote that corresponds to their UUID.
BTW, thanks for engaging in this discussion. It's important and it's helping me rethink through all of this.
Another option is making a fake ballot. The local newspaper used to helpfully publish their suggestion of how a devout left wing progressive would fill out their ballot. They're currently the establishment, so they're likely to be the largest problem, and its solved right there.