First and fore most file a police report.

I have gone through this same thing about a year ago. Son had his phone stolen from a skate park. The kid who stole it, used my son's phone to text a person and the record of the text was on his phone records from his provider. I filed a police report and it was closed almost immediately due to lack of evidence. So I called the person that got the text after the phone was stolen and they gave me his name. The person also set up a meeting with the thief at a local convenience store. I called the cops and had them respond. They took his name and let him go, due to lack of evidence. So of course I found more evidence against this thief. I was able to put him at the place the phone was stolen, who he was with, the text from the phone to the other person, and found a witness to the theft who signed a statement stating the kid stole the phone. Basically you have to make the case for the cops before they will act.

So gather as much evidence as you can, the photos are a great start, then get her attendance record that she was at work the same time the phone was stole. If the GPS tracker is installed the get the location of the phone. Get any call or text records from your phone provider and track down the people she called with the stolen phone. This will prove she has or had possession of the phone. Then take all the information back to the cops for them to file charges. If it all goes well, then they will issue a contact warrant. If she is contacted within 30 days by the cops, they will issue the person a Notice to Appear in court for the charge of theft.

You will have to do all of the work to prove the case, so gather as much evidence as possible to make the case. The cops will treat it as "just another stolen phone". They will put little or no effort into making the case. I do understand that with so many phone lost or stolen phones they could not possibly pursue every one. So you have to do it for them.

In my case, I got the kid to plead guilty to theft and had to repay the total cost of the phone, case, and reactivation charges. This all took about 6 months but my son got a very valuable lesson not to leave his phone laying around, and there are some bad people (thieves) out there and perseverance does pay. I even got a job offer from the city attorney as a private investigator.