A football fan seems to have vanished into thin air from an NFL game last week in Denver, reports 9NEWS.

Paul Kitterman, 53, his step son, Jarod Tonneson, and their two friends attended the Oct. 23 game between the Broncos and the San Diego Chargers.

According to authorities, Kitterman and Tonneson left friends in two different stadium sections during the game. The father and son met at half time near the Level 2 concession stand on the stadium's southeast side.

"Jarod went to go to the bathroom and the third quarter was starting so we told Paul, 'Well Jarod's going to be right back, and we're going to go to our seats,'" friend Tia Bakke told 9NEWS. "Paul's like, 'Yeah, yeah. We'll see you after the game."

Kitterman never returned to his seat. Tonneson thought he had gone with friends to their seats, so he didn't think twice about it.

The game ended. The friends convened. There was no trace of Kitterman. The friends stayed at the stadium until 1 a.m. searching for him. When he wasn't found, the family filed a missing person report with the Denver Police Department.

Kitterman did not carry his credit cards or have a cell phone at the game, the family said.

His family and friends called police stations, local hospitals and detox centers but couldn't find Kitterman. The family said such behavior is uncharacteristic of Paul, who has no history of drug use, dangerous activity or medical condition.

Denver Police detectives are reviewing surveillance camera video from the stadium, according to 9NEWS.

Surveillance video could tell police when Kitterman was last seen at the stadium, what his demeanor was like the last time he was seen and who he might have spoken to or been with.

"At this point in time we don't see any foul play that we are aware of, where he might have come upon harm, but we don't know at this point," Sonny Jackson, a Denver Police spokesman, told 9NEWS.