I didn't say there was no paper trail. I said there no ballots. That is a subtle difference that if you don't go to democrat caucus in Iowa you probably don't understand.
Theoretically a group can win delegates in a caucus with just an issue not a candidate - for example you can all agree that the most important issue is Oranges (a fruit that doesn't grow in Iowa...) and get a delegate without committing to a president. Of course in practice most people show up only for the president poll and leave as soon as that is over.