The school office checked every delivery record from Friday.
One company had brought new music stands and several boxes of printed concert programs.
The driver remembered the visit because the side door had been difficult to close.
He also remembered taking one extra black case from the corridor by mistake.
He had thought it was an empty protective case that belonged with the delivery equipment.
At the warehouse, workers searched the returned boxes.
They found no violin.
The driver then remembered that the extra case had not reached the warehouse at all.
After leaving the school, he had stopped at a community centre to deliver chairs for an evening event.
Several empty cases and boxes had been unloaded there together.
Karim, Mr Lewis, and the police officer went to the centre immediately.
In a locked storage room, they found three black cases beneath a pile of folded tables.
One of them was shaped exactly like the missing violin case.