He did show the pamphlet DHS provided mentioning dhs.gov/dhs-trip on the stream.

Edit :

DHS themselves admitted there was an "inspection" but not much beyond that.

When asked for comment about Piker, a Department of Homeland Security official called his account “nothing but lying for likes.”

“Claims that his political beliefs triggered the inspection are baseless,” Assistant Secretary Tricia McLaughlin said in a statement. “Our officers are following the law, not agendas. Upon entering the country, this individual was referred for further inspection — a routine, lawful process that occurs daily, and can apply for any traveler. Once his inspection was complete, he was promptly released.”

https://www.nbcnews.com/news/us-news/hasan-piker-twitch-streamer-questioned-us-customs-rcna206406