And what is that?
What is the protocol they follow here, and did they follow it correctly?
Are you in a position to even know this?
Could it be possible they did do everything, and you're just not aware, as you are rightly concentrating on your loved one and hopefully trusting them to take care of their end?
I understand you're frustrated, but if the lines of enquiry don't produce anything, what can they do?
It can be a common misconception that just because there is CCTV, lines of enquiry, witnesses, etc., it will lead to arrests; unfortunately, it doesn't always produce enough results for the identification and arrest of offenders. Sometimes investigations can fall flat very quickly.
It can be very hard for victims to accept due to the trauma and upset at what they have experienced, which is very understandable, but it doesn't mean they didn't do their job and try.