Lost something valuable to my mom and now she's upset. What do I do?

Okay, so my friend that moved away came to visit my school today. It was drizzling today so my mom dropped off her special umbrella at the office. When it was lunch time I picked it up and put it on the bench where my friends eat because at that time it was not drizzling anymore. I was so distracted with my friend that I left it there on accident. During the class I had right after lunch, I realized this and as soon as it ended, I looked to see if it was there, but it was gone. After school, I looked in my locker, in my backpack, in the lost in found, but I had not luck. I have already lost my phone before and my locker keys, so I don't know why my mom dropped off her ultra special umbrella for me if she does not trust me. It is special to her because she bought it five years ago in Italy on her honeymoon with my step dad. I told her as soon as she got off work and I tried to apologize, but she started yelling at me and slammed her bedroom door and started crying. Now I have no idea what to do. Please, someone help me!!