Keenum stayed in the game after showing the effects of his head being slammed to the turf on the Rams' final drive. His lost fumble two plays later ultimately cost the Rams the game.
According to the St. Louis Post-Dispatch, a Rams official told the media 25 minutes after the game that Keenum couldn't speak with the media because he had suffered a concussion. The team's website reported the concussion as well.
The Rams told NFL Media on Monday that coach Jeff Fisher would address the issue at his weekly press conference.
The NFL instituted a new rule in 2015 in which a "spotter" at every game has the power to stop play if he sees any player struggling with a potential concussion.
It seems baffling that Keenum wasn't at least checked out after this incident: