What should I do about this cell phone problem with my best friend?

So my friend karen got into my locker (she knows my code) and karen wrote a message on my phone and took a picture of herself for it, and im fine with that then my friend arden came and said can I see the phone and karen said sure and let arden use it and then at the end of the day (I knew arden had my phone) I said arden do you have my phone, can I have it back? Arden said she didnt have it and she said she gave it to my friend lily so I went to lily right away and said do you have my phone and she said no she doesnt and I went back to arden and arden said I dont have it , karen has it! So I went to karen and she said that arden has it but she passed it on to people and then I said omg because I just like ran around the school so I went to find arden but she was no where to be seen so I went home and like my parents were angry at me and stuff and karen appologized to me and said she didnt mean to give arden the phone and I told karen that it wasnt her fault, she didnt lie. The next day when I got my samsung phone back arden didnt say sorry so I ignored her and then she said sor-ry I was looking for you. No she wasn’t??? Should I tell the office? What should I do? Please help.