I am writing a story and in it my main character gets a phone call, which is witnessed by her mum and she lies and says it’s somebody else and she goes cheap pills online out to meet the person who called and he murders her. My question is would the cop investigating her death know if my character got a mobile phone call that night and if they could trace the real person it is from, even if the mobile phone is missing [or otherwise the murderer destorys the battery.]

Thanks. It’s a hole in my story if this doesn’t work.