At our polling place, you get a little printout with your voter information (name, address, DOB, affiliation) when you check in, take that to a volunteer who gives you a ballot in a paper folder with a sleeve outside for the printout, go fill out the ballot at a table with privacy shields, put it back in the folder, take it to the scanner, hand the folder with the printout to the volunteer, then you feed the ballot to the scanner.

So the volunteer at the scanner doesn't see how you voted; collecting the printout from the now-empty folder is how they verify you.