My boyfriends ex stole my iPhone, what can I do?

Last Thursday night I was at my boyfriends house, which he used to share with his ex. At about midnight she entered the property which she is still on the tenancy for but no longer lives there, we didn't hear her enter the property but heard her slam the door, she then came into the sitting room where she shouted and swore for me to get out of the house, she also told me I'm still lucky to have my job (she's a manager at the place where I work) I promptly left the house grabbing my handbag which was in the hallway but as she was chasing me out of the property I didn't go into the kitchen where I had left my phone on the left by the cooker. I then drove home and facebooked my boyfriend that I had left my phone in the kitchen and he then replied saying that it had gone, I went back after she had left and called the police. I haven't yet gone back to make my formal statement I have just reported it. I know my phone was 100% there and after she had entered the property it had gone but I have no proof it was her, what are my rights? What can the police do? Help!