Their current stance was not a terribly powerful one. In a real fight, this would be a problem, in fact.
The only thing they could think of to do was to start to swing the fallen end of the staff up so they could grab hold of it with their free hand. That enabled them to adjust their grip of the other hand so the staff was now back in sort of longsword formation and they brought it down as hard as they could.
Even done quickly, it was inelegant, but at least at the end of it, they were back in the fight, more or less.
The only thing they could think of to do was to start to swing the fallen end of the staff up so they could grab hold of it with their free hand. That enabled them to adjust their grip of the other hand so the staff was now back in sort of longsword formation and they brought it down as hard as they could.
Even done quickly, it was inelegant, but at least at the end of it, they were back in the fight, more or less.