Is it possible to see one's location if they removed the app without signing out first?

A friend of mine invited me to use find my friends. He followed me and I followed him back. One day, I could no longer see him in my followers list yet I was still able to see his location and it would update all the time whenever he changed location. When I asked him, he said he deleted the app. How was I still able to see his location if he deleted it? He had it on hos iPad and iPhone and he deleted it from both but I was still getting his accurate location. Is that even possible?