Not absolute proof, but the beginnings of it: https://noqreport.com/2020/11/07/the-hammer-and-scorecard-smoking-gun-150000-michigan-presidential-voters-didnt-vote-for-senate/
There are similar reports from GA, PA, AZ and NV.
Even if those people voted, I would interview them, if possible, to still figure out who they are. They might have been paid to vote. Harvested. It used to happen in my area of Texas.