Find my phone stopped showing the last location of my stolen iPhone.

My son had his iPhone stolen in January. Find my phone was working and I could see its last location before it ran out of power. It took a couple of weeks for my son to accept that the phone would not be found or returned, but when I listed it as stolen in Find my phone and started the insurance claim. AIG claimed that Find My Phone had been turned off in October the previous year. When I went to Find My Phone the last location was no longer being displayed. How long does Apple keep location data and how would I ask for it?

Thanks