Someone stole my ray bans?

My bus switches to another bus sometimes.. And i left my ray ban on the seat with the case.. i went to school and i didnt really realize i left them there. until i was halfway home and my bus driver called the other bus driver ans she didnt see them and im postive i left them on the bus ao i stalk the bus for a week and they didnt see anything lies i went to lost and found nothing ... my friend that i talk to in the morning was wearing ray bans today and my other friend was like the one who was wearing ray bans friend said she found them and gave it to her for free and i asked if i could see them and i had the same wear of the made in italy i really think there mine how do i get them back or confront the girl