A laptop was left by someone in the cafeteria this morning.
It was found by another student and it was given to the teacher (by her).
The owner was asked (by us) to come to the headteacher's office to collect it.
A lot of electronic gadgets were lost by students last month.
Several of these were not returned to the owner by us, because the owners were not found by us.
You are reminded (by us) to be careful with laptop computers and smartphones.