Bowman, who originally suffered the injury against West Virginia on Sept. 29, directed the Red Raiders to a 31-28 halftime lead over seventh-ranked Oklahoma, but he took a hard hit from Sooners linebacker Curtis Bolton late in the second quarter and was unable to start the second half.
Head coach Kliff Kingsbury said Bowman was having difficulty "catching his breath" during warm-ups before the start of the second half. Bowman then returned to the locker room with Texas Tech athletic trainers and medical staff.
Kingsbury dismissed initial reports that Bowman had been injured when he was struck in the head with a football during those warm-ups, saying, "It wasn't anything with his head."
Following the coach's news conference, Texas Tech issued a statement saying Bowman had been transported to Lubbock's Covenant Medical "to be evaluated for a recurrence of his previous injury (partially collapsed lung) that occurred in the West Virginia game. He will be held overnight for observation."
Bowman was still in the hospital as of Sunday night, according to the school. On Monday, Kingsbury said the situation was "kinda day-to-day right now.
"The main focus is on getting him better and healthy."
Jett Duffey took over for Bowman at quarterback. After a slow start, the sophomore threw two touchdown passes and ran for another score, nearly leading Texas Tech to the upset.
The Sooners won 51-46.