One proof of wrongdoing would be if the thumb drives result in more votes than registered voters, even taking in to account the fact that not all registered voters vote.
There have been more than a few elections in the past that have had more votes than than the entire adult population of the county, registered voters or not.
democRATic stronghold, Broward County, in south Florida comes to mind.
100%+ voter turnout. No one ever challenged it.