Note that “typing the answers into a computer” doesn’t necessarily mean that the answers went anywhere. This may have been pure security theater with the computer acting only as a tool of intimidation, rather than actual data collection. If so, DHS could be telling the truth about not having any records of the incident.
In which case the question would then become one of why the DHS agents in question thought this was a good thing to do to these individuals. I grant that this isn’t as satisfying to object to, but arguably it’s a more important question.